Why do many Buddhists hold on to views?

In the famous Parable of the Raft, the Dharma, as well as that which is not the Dharma, is something that is discarded at the far shore. The Dharma is for crossing, not for clinging. Some, when they hear that the Dharma is for crossing and not for clinging, wish to discard their raft so as to not cling to it. What is your raft? The teachings of the Buddha are your raft. The threefold training is your raft. The eightfold path is your raft.

If we discard the "view" that there is a threefold training, if we discard the training before the crossing, then how will the raftless swimmer cross, rhetorically speaking? The point of the Parable of the Raft is not to swim raftless to the far shore. Swimming raftless, swimming "Dharma-less," swimming "viewless" isn't presented as a possible solution to the problem posed by the parable, namely the problem of a "great expanse of water" that is "dubious & risky" at the near shore (from MN 22 as translated by Venerable Ṭhānissaro). The raft is needed in the parable because forgoing it is simply not a viable option. Otherwise, IMO the point of the parable becomes obscured.

This addresses the issue of "all views" and whether we need to discard "all views" in order to reach the far shore. The Parable of the Raft, to the extent that it can be construed to refer to dropping "all views," has this happen once the far shore has already been reached.

What about other views?

One makes an effort for the abandoning of wrong view & for entering into right view: This is one's right effort. One is mindful to abandon wrong view & to enter & remain in right view: This is one's right mindfulness. Thus these three qualities — right view, right effort, & right mindfulness — run & circle around right view.

(Mahācattārīsakasutta MN 117 translated by Venerable Ṭhānissaro)

What about in the Abyākatasutta, where spiritual progress is associated with "the cessation of views" ("diṭṭhinirodhā")?

Because of the cessation of views, monk, uncertainty doesn’t arise in an instructed disciple of the noble ones over the undeclared issues. The view-standpoint, ‘The Tathagata exists after death,’ the view-standpoint, ‘The Tathagata doesn’t exist after death,’ the view-standpoint, ‘The Tathagata both does and doesn’t exist after death,’ the view-standpoint, ‘The Tathagata neither does nor doesn’t exist after death’: The uninstructed run-of-the-mill person doesn’t discern view, doesn’t discern the origination of view, doesn’t discern the cessation of view, doesn’t discern the path of practice leading to the cessation of view, and so for him that view grows. He is not freed from birth, aging, & death; from sorrows, lamentations, pains, distresses, and despairs. He is not freed, I tell you, from suffering & stress. But the instructed disciple of the noble ones discerns view, discerns the origination of view, discerns the cessation of view, discerns the path of practice leading to the cessation of view, and so for him that view ceases. He is freed from birth, aging, & death; from sorrows, lamentations, pains, distresses, and despairs. He is freed, I tell you, from suffering & stress.

(Abyākatasutta AN 7.54 translated by Venerable Ṭhānissaro)

This sutta, complete with its section on the "cessation of view," is dealing with particular views ceasing. In particular, it deals with four views that it outlines in the body of the sutta. 1) That ‘The Tathagata exists after death,’ 2) that ‘The Tathagata doesn’t exist after death,’ 3) ‘The Tathagata both does and doesn’t exist after death,’ and 4) ‘The Tathagata neither does nor doesn’t exist after death.’ It is due to the cessation of these views that "uncertainty doesn't arise," to use the language from the sutta directly. So we can see that the Abyākatasutta does not actually instruct the followers of the Buddha to abandon all views in toto, including the right ones. This is, however, a common way to read the sutta in my experience even if it is mistaken IMO.

It is crucial because it is one of the 4 primary fears necessary for proper motivation.

“Mendicants, there are these four fears. What four? The fears of guilt, shame, punishment, and going to a bad place.

And what, mendicants, is the fear of rebirth in a bad place? It’s when someone reflects: ‘Bad conduct of body, speech, or mind has a bad result in the next life. If I were to do such bad things, when my body breaks up, after death, I’d be reborn in a place of loss, a bad place, the underworld, hell.’ Being afraid of rebirth in a bad place, they give up bad conduct by way of body, speech, and mind, and develop good conduct by way of body, speech, and mind, keeping themselves pure. This is called the fear of rebirth in a bad place. - AN 4.121

It is most fundamental to how The Buddha trained people;

"Kesi, I train a tamable person [sometimes] with gentleness, [sometimes] with harshness, [sometimes] with both gentleness & harshness.

"In using gentleness, [I teach:] 'Such is good bodily conduct. Such is the result of good bodily conduct. Such is good verbal conduct. Such is the result of good verbal conduct. Such is good mental conduct. Such is the result of good mental conduct. Such are the devas. Such are human beings.'

"In using harshness, [I teach:] 'Such is bodily misconduct. Such is the result of bodily misconduct. Such is verbal misconduct. Such is the result of verbal misconduct. Such is mental misconduct. Such is the result of mental misconduct. Such is hell. Such is the animal womb. Such the realm of the hungry shades.' - Kesi Sutta

Being without this fear is closest to trying to train without fear of shame, guilt or any fear of punishment. What do you think, is it important?

Added;

that the Buddha doesn't teach what the universe is like, but rather about the mind.

These can not be separated because The Buddha clearly taught about the origin on the world as well as mind eg DN27 Genesis.

The whole notion of escaping samsara without rebirth is pointless without rebirth because one can just wait to die as death makes equal.