Why does 'thoughts' and 'memories' not part of aggregates?

I will answer based on the early buddhist texts.

Memories & thoughts are perceived [sanna] and that due to contact at mind-base, contact therein is between that which is called "consciousness, mind or intellect" and ideation.

The Blessed One said, "What is the All? Simply the eye & forms, ear & sounds, nose & aromas, tongue & flavors, body & tactile sensations, intellect & ideas. This, monks, is called the All. [1] Anyone who would say, 'Repudiating this All, I will describe another,' if questioned on what exactly might be the grounds for his statement, would be unable to explain, and furthermore, would be put to grief. Why? Because it lies beyond range." https://www.accesstoinsight.org/tipitaka/sn/sn35/sn35.023.than.html

The intellect disintegrates. Ideas disintegrate. Consciousness at the intellect consciousness disintegrates. Contact at the intellect disintegrates. And whatever there is that arises in dependence on contact at the intellect — experienced as pleasure, pain or neither-pleasure-nor-pain — that too disintegrates."Insofar as it disintegrates, it is called the 'world.'" https://www.accesstoinsight.org/tipitaka/sn/sn35/sn35.082.than.html

Ideation is conceived & perceived by mind which arises as one thing and ceases as another.

what's called 'mind,' 'intellect,' or 'consciousness' by day and by night arises as one thing and ceases as another. https://www.accesstoinsight.org/tipitaka/sn/sn12/sn12.061.than.html

Sankhara is that which creates mind as mind, ideation as ideation, mind-base as mind-base.

“And why, bhikkhus, do you call them fabrications? ‘They fabricate the conditioned,’ bhikkhus, therefore they are called fabrications. And what is the conditioned that they fabrications? They fabricate conditioned form as form; they fabricate conditioned feeling as feeling; they fabricate conditioned perception as perception; they fabricate conditioned fabrications as fabrications; they fabricate conditioned consciousness as consciousness. ‘They fabricate the conditioned,’ bhikkhus, therefore they are called fabrications. SN 22.79

Contact is requisite condition for feeling, what is perceived that is also felt, what is felt is also cognized, these [feeling, perception & conciousness] are conjoined.

"Feeling, perception, & consciousness are conjoined, friend, not disjoined. It is not possible, having separated them one from another, to delineate the difference among them. For what one feels, that one perceives. What one perceives, that one cognizes. Therefore these qualities are conjoined, not disjoined, and it is not possible, having separated them one from another, to delineate the difference among them." https://www.accesstoinsight.org/tipitaka/mn/mn.043.than.html

Felling, perception & consciousness are also conjoined with Sankhara because that which is felt and to that extent cognized & perceived, that is likewise also generated.

Three aggregates are conjoined with consciousness. The aggregate of form is not conjoined with consciousness. The aggregate of consciousness should not be said to be conjoined with consciousness or not conjoined with consciousness. https://suttacentral.net/vb1/en/thittila

Therefore thoughts & memories are included in aggregates.

Emotional thoughts and mental chatter are part of sankhara or mental formations or mental fabrications. The OP's translation calls this "choices".

It appears that memory is related to the aggregate of perception. Please see below.

From The Abhidhamma in Practice by N.K.G. Mendis:

Perception (saññaa)

Perception is awareness of an object's distinctive features. It becomes six-fold in relation to the five physical sense objects (color, sound, smell, taste, touch), and mental objects. It is sañña that enables us to recognize an object previously perceived. .....

Perception and memory. Memory occurs not through a single factor but through a complex process in which perception plays the most important role. When the mind first cognizes an object through the senses, perception "picks out" the object's distinctive mark. When the same object is met with on a subsequent occasion, perception again notices that its distinctive mark is identical with the previous one. It "grasps" the identity of the distinctive marks. This "grasping" is a complex series of thought processes, one of which connects the present object with the previous one and another attaches to the present object the previous one's name. Memory will be good if this "grasping" functions well, and "grasping" will function well if the initial "picking out" of the object's distinctive marks was clear, not obscured by irrelevant thoughts. Clear perception comes through attention. As the Buddha says: "In what is seen there must be just the seen, in what is heard there must be just the heard, in what is sensed there must be just the sensed, in what is thought there must be just the thought."

By the way, feeling as an aggregate does not refer to emotions, as the OP implies. It refers to sensations as in feeling pleasure and pain from the six senses - eyes, nose, ears, tongue, body and mind.

From the same source:

Feeling (vedanaa)

In the Abhidhamma context the word "feeling" signifies the affective experience of an object; it does not imply emotion, which comes under a different heading. Feeling is associated with every type of consciousness. Like the citta itself it is of momentary duration, arising and perishing in an instant. This arising and perishing occur in rapid succession, so much so that they create an illusion of compactness and stability obscuring the momentariness. But the momentariness can be experienced through the practice of mindfulness. It will then be realized that there is no self or agent that experiences the feeling. There is only the arising and disappearing of an impersonal process. As long as we do not see how this impersonal process occurs we will be led to believe that feeling is the self, or the self possesses feeling, or feeling is in the self, or the self is in feeling. These beliefs keep us bound to suffering — to sorrow, lamentation, pain, grief, and despair.

Feelings are commonly classified into three types: pleasant, unpleasant, and neutral.

Let's take an example. There are a bunch of roses in a vase in a restaurant. You see them - this is feeling or sensation. Then based on your past memories, you perceive it as roses. Oh... but then it reminds you of your ex-lover to whom you used to give or receive roses. Then the mind feels or senses the mental object of your ex-lover and his or her association with roses, and perceives it to be memories of events of the past. Then you start having emotions of sadness and start the mental chatter of negative thoughts about your ex-lover. That's part of mental fabrications.

It's all included, it's just a slightly different structure.

Latent memories just sitting there are included in "samskara" (what's incorrectly translated as "choices" in your copy).

Active memories you are going over now are included either in "perception" (as associations to whatever you perceive)

Or in "form" if, for example, you are visualizing a piece of memory, creating forms in front of your mind's eye.

The way mental stuff is organized in Buddhism is a bit more technical than in our civilization. So instead of calling bunch of different things "thoughts", Buddhism gets more specific and classifies things according to how they work.

Thinking is going through a chain of associations, so each thought is a (mental) form, then it goes through perception (supported by latent memories), which finds next association, which then becomes the new form etc.