Most people are followers.

They don't invent own projects. They find existing projects to copy. They may wiggle a bit and make minor changes after having the duplicated project up and running.

So the Arduino eco system is basically a rather large library of more-or-less turn-key solutions. It's (to a large part) for people with lack of imagination.

Looking for other dev-kits means you need to use your own imagination to figure out what you can do. And how to do it. But these people who can do that will not spend so much time (or any time at all) asking questions on web forums.