I think this is exactly it. I had never even heard of Lemmy, and its structure, along with Mastodon's (I'm not even sure how equivalent these two platforms are), are a bit alien. So I think, at least among people who are more familiar with message boards and the like, that's th path of least resistance. Not that it's actually difficult to register, but I can see why there may be such a perception.

That's how I discovered this space - someone posted about it in the Autechre sub.