If the registration process just picked a random instance for you, maybe something nearby, and assured new users that they can visit communities and interact with users across instances, very few would pick the biggest instance.
That isn't guaranteed, though. The other day I wanted to create a new community and was browsing instances on join-lemmy.org/instances for an instance that was compatible rulewise. The one I picked evidently wasn't a good pick (burggit.moe). Trying to advertise my new community, I found out it was defederated from beehaw (and likely others) and got insulted as a pedophilia sympathizer ...
Randomly assigning new users to instances would make a substantial fraction of people very unhappy.
If the registration process just picked a random instance for you, maybe something nearby, and assured new users that they can visit communities and interact with users across instances, very few would pick the biggest instance.
That isn't guaranteed, though. The other day I wanted to create a new community and was browsing instances on join-lemmy.org/instances for an instance that was compatible rulewise. The one I picked evidently wasn't a good pick (burggit.moe). Trying to advertise my new community, I found out it was defederated from beehaw (and likely others) and got insulted as a pedophilia sympathizer ...
Randomly assigning new users to instances would make a substantial fraction of people very unhappy.