Why is there so little emphasis on "mundane" mindfulness?

Buddha taught dāna, sīla, and bhāvanā for a layman, and taught sīla, concentration-bhāvanā, and insight-bhāvanā for a monk.

So, general “mundane” mindfulness is sīla, virtual. There are many sutta that teaching you to practice virtual mindfulness.

But, concentration-bhāvanā and insight-bhāvanā are the mundane path to leave out the whole mundane. Because the natural mundane is five strands of sensuality, that the practitioner try to leave out first by concentration-bhāvanā. And the supernatural mundana is concentration-bhāvanā, that the practitioner try to leave out by insight-bhāvanā. See mahādukkhakhandhasutta for more information.

In detail as abhidhamma, concentration-bhāvanā and insight-bhāvanā still being mundane, lokiya, just magga, phala, and nibbāna are super mundane, lokuttara.

Note: super natural mundane, lokiya, is not super mundane, lokuttara.

What gives? Are the practical, mundane benefits of mindfulness simply not emphasized, and if so, why?

The Buddha's Teaching is about ending suffering completely, ie. to reach Nibbana. Sure there are mundane benefits but that is not really the goal of following the Noble Eightfold Path. Freeing oneself from the cycle of rebirth is.

Couldn't finish the linked article. Mindfulness, either this is a wrong etymology for the Buddhist practice; or, if accepted it's the term, than the technique told by those marketers were wrong.

Wrong etymology: this Buddhist practice, in Chinese: 繫念, doesn't simply mean mindfulness. It means rein in the mind, and fasten it to the present moment. Ever since the so-called Vipassana Movement let out by Mr. Goekna in his croaky videos in his centers, declaring "Dhamma this... Dhamma that", the secular meditation world is obsessed with body scanning; and from body scanning to scanning the body touching the chair... scanning chair touching the body, called mindfulness... as described in the linked article :).... 囧. (speechless)

When taking photo of fast movement, if chasing the movement the photo will always be taken one second behind. The right method is anticipating led to one second ahead of the movement triggering the shutter. How does it work? If one reined in the mind, fasten it to the present moment, one will act one second ahead. Chasing the movement is reaction; capturing the movement is action, achieved when the mind is empty and ready.

The car key things maybe are mindfulness, but can be achieved with minimal of strict Buddhist [meditation of mindfulness] practice. It's just be heedful, pay attention sort of can arrive there. Perhaps that's why these mundanes (benefits) not emphasized. Of course it would be good if mindfulness is a minute to minute, second to second habit - an accomplished master mastered, like the Buddha did. For instance, those older ladies doing dancing in the piazza after dinner, they are doing kind of Chacha, Salsa... but it's not the same as a professional doing Tango, or Ballet. The emphasis for dancing in the piazza is the benefit of health; the Tango performance is the art. It will confuse people if one teaching Tango, but emphasizing the benefit of health. Mindfulness practice marketed maybe are largely corrupted practice of mindfulness, got the name only.

Yet in a strict training environment, all acts are types of training; like Martial Art, even using chopsticks picking up the rice, is training of Neigong. I just read in the Chinese Vinaya, due to certain accidents, the Buddha set out discipline of mindfulness going washroom:

佛言。不應散亂心上廁。散亂心上廁突吉羅。今為諸比丘制上廁等初應學法。是中比丘應盡形壽學。若不學突吉羅... (shouldn't be mindless/heedless when going to the washroom, or else committed Duṣkṛta)

若比丘上廁時應一心看前後左右。至廁前欬彈指令廁中人非人知。廁中人亦應彈指欬。既入廁復應看前後左右仰視屋間。無蛇蚖毒虫不。不應以衣突戶兩邊。好收歛之一心安足。勿令前却以污廁上。若先有污及己所污皆應治事。須洗洗之。須拭拭之。須除草穢除之。然後出去。徐下護衣勿使污穢。往小便處及洗大小便處亦應如是。若用水時。應先看水有虫無虫。不得多用水。然要使周事。以器捲水極令安徐。不得使器相撐以致破損。用水若盡。應更取使滿。若有急事。要應取令得一人用覆頭 而去... (a detail step to step instruction, from snapping the finger to acknowledge, to arranging the clothing... using the water... etc., there were additionals when some Bhiksus violated the basic setup)

Example, Mahisasakas Pratimoksa (survived only in the Chinese Canon) recorded an event, Buddha and his Bhiksus were invited by a famous courtesan to her manor for the meal. When setting out, Buddha reminded the Bhiksus, "繫念在前" (reined in and fasten the mind to present, or be mindful), because they were about to enter into a house of great temptation. In this event, the mindfulness, contrast to the marketers' advice, doesn't have an object to be mindful of. Another example, also in the Chinese Vinaya collection, recorded when Devadatta stolen 500 Bhiksus from the Buddha to set up his own Saṃgha, Sariputra and Maudgalyāyana sent by the Buddha visiting him. Devadatta, thinking they were coming to join him, mimicking the Buddha, ordered Sari. to deliver the teaching while Maud. do the Rddhi show, said his back was kind of aching (like the Buddha's back), then laid down on his right for a rest (also like the Buddha did). However, he forgot to "繫念在前" (be mindful) (the Buddha always did) soon fell asleep, snoring noisily and drooling, when the two led away the 500 Bhiksus. Here again, there would not be any object to be mindful of if Devadetta really practiced mindfulness to prevent fallen asleep.

According to records in Chinese Canon, if mindfulness - 繫念 practiced correctly, one will easily be a genius, from simply having photographic memory, to preforming psychokinesis.