Because nobody knows they exist. Especially not on Mastodon. And even less outside the Fediverse, tech media included.

And truth be told, way too many Mastodon users don't want to know. They want the Fediverse to remain what they thought it was when they joined: only vanilla Mastodon.

Really goes to show that Lemmy is full of tech-curious geeks: Tell a Lemmy user about a Fediverse project that's neither Lemmy nor Mastodon, and it's much more likely for the reply to be something along the lines of, "where public instances."