Stories are great for the platform. They drive user engagement, and, hence, advertising.
As far as I can tell, they're terrible for the users. You have to constantly be active to not miss something, you can't just check back in after a few days. For some reason, comments are private only, which is almost never what I want -- as a poster, as a commenter, or as an observer. Contrast that with (say) a "normal" IG/FB post of a picture from the beach, where comments are public and a community of people and comment on it and reply to each other in a social way. Stories are basically broadcast-only. They're also MUCH more time-consuming to create.
I've only done a few stories, always when traveling solo, so I have time to kill and it was useful to learn something new the first time. The only positive thing I can say about them is that, because they're ephemeral, I feel less bad about posting some stupid snapshot of something unimportant/trivial.
That this is coming to Twitter is even more concerning, because it's already the most shouty, least-community driven social network, with the largest multiplier on saying trolling/annoying/controversial/stupid things in the pursuit of clicks and likes and retweets.