FOMO for sure is one of the driving factors.
"We cannot risk looking outdated". So weak management, probably.
But also talent availability I suppose. If there's a new trend, the pool of people you can hire include many that are in on that trend.
UI frameworks too, probably. The modern thing™ does the modern thing™ and you do want to be on the modern thing, because you fear that only that receives security fixes or whatever.
I really don't think that "keeping people entertained" is a sensible goal within the context of building software as tools and not software-adjacent Art.
Which is not to say that I would not want a great and polished experience, but that is not equivalent to "being entertained".
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It would be nice if not everything one interacts with would try to get some sort of emotion out of me. Bring back being bored.
I don't think I know any non-tech people who like things changing about. Some tech people like that (I don't), but for the non-techy, it's just another thing they have to relearn for no good reason.