From what I've seen of the emulation community, I can only think it's because many emulators are small enough that they're feasible for a single person to work

From what I've seen of the emulation community, I can only think it's because many emulators are small enough that they're feasible for a single person to work on and maybe get too attached to. It's difficult to let go of your code baby, especially when you could technically do it all on your own. It's probably easier when the task is so large there's no way you could do it alone