I don’t fully understand how lemmy works completely yet. But for example I made an account at Division by zero and subscribe here to post. Is it not just a more inconvenient version of making a reddit account and being able to post practically anywhere?
Also what’s the difference between making an account at one instant and just making one centralized account for the social media?
On the contrary, a bunch of scattered communities create one large user base. The people you see in this thread all come from a bunch of different websites and services. You’ll see users from startrek.website discussing woodworking in communities hosted by lemmy.ca.
On top of this, someone could make an instance dedicated to that niche subject and similar topics, and you could subscribe with the account you already have somewhere else instead of having to periodically check that niche instance.
Right now the problem is finding those instances, and generally finding reliable instances that won’t suddenly go offline