For me, the reason is easy: my writing is horrible. I learnt cursive at school (and my children are learning only cursive at school, cursive is not disappearing in France at all) so it's not the problem. I'm creative, but clumsy, so the typewriter is the perfect solution for me. Moreover, I have ADHD, so I need things to “launch” me if I want to do something. Often the typewriter do the trick. And there's a pleasure in the act of typing that i don't feel with a computer or a pen.

But maybe it could be a self standing post instead of a comment? You'd have more answers.