I don't think they're trying to draw users in yet? It's invite only isn't it?
It doesn't matter how attractive a platform is if you simply aren't going to get onto it. Clubhouse can make me interested, but can't actually get me onboarded.
I can imagine a scenario though, were they gradually increase the number of invites they give out. I think the idea is that the perception of scarcity will persist, even when invites aren't really scarce.