I guess it’s a matter of someone collecting the information. The side bar of the community has active user stats for the community, and I think that should be just as accessible as instance stats.
But sites have been around a long time collecting mastodon and other fediverse stats, and communities don’t really exist there. So stats sites don’t seem interested in collecting the community info in Lemmy.
I think it’s likely doable, just I haven’t found anyone actually doing it.