@GoldenDoge Because it is a topic-oriented access to the Fediverse.
I don't have any experience with #Reddit or similar, but rather like that it's a kind of forum where the content is a bit more sorted than in the micro-/macroblogging software. Nevertheless, everyone with accounts from #Misskey, #Mastodon, #Friendica, #Hubzilla etc. can also comment and create posts in #Lemmy communities. So the circle of users is much larger than just Lemmy alone.