I would argue their main motivation for keeping iOS separate from MacOS is that it's much more locked down. If they were to try to merge the two, they would either have to give up a sizeable portion of revenue from their app store and advertising monopolies on iOS, or handicap MacOS making it much less competitive with laptops that actually treat you like the owner of your own hardware. But if the EU is successful at tearing down a few more of the iOS garden walls, Apple may start to think convergence is a good idea.