I started it because I recognized that it took entirely too long to implement some of the most basic core functionality for cross-platform apps in a way that is up to my standards (i.e., minimal with no real vendor lock-in). It actually boggles my mind that nothing of the same quality as Molecule.dev exists yet. It's obviously a problem that developers everywhere run into when building custom apps. I've seen a few solutions, but (again) they're all either not up to my standards or they try to lock you in.
I think most developers prefer to implement things themselves, as they have their own preferences and may (like me) not trust that the code quality is up to their standards, so the difficult part here may actually be to convince developers that the code is high quality and something they themselves would write.