One reason is to move from being the product to being a user, so that your attention is not sold to the highest bidder and your behaviour manipulated in such a way that it produces the highest value. Of course, paying with your attention is a valid way of paying for things as long as the implications are clear.

edit: spelling mistakes

Censorship resistance. Twitter could delete your account (or some of your tweets) if they wanted to. They could also prevent your tweets appearing in other people's feeds. And they have done this to some controversial figures.

Basically a Dapp is a more neutral platform that costs money. Probably not worth the cost for the average person though.

Unless you are involved in neo-nazi organizations or narcotics distribution, i do not see it either.

You definitely shouldn't!