That's presumably an anti-bot/astroturfing measure. As bad as that is, I'm not sure what the alternative should be. Allowing anyone to post with a 1 minute old account? Implement real name verification?
I can't speak to every local subreddit but I can tell you for sure that while it may have started as an anti-bot measure, on /r/newzealand it is absolutely used as a way to gatekeep the wrong opinions from being present on the subreddit.
Using the 1/9/90 split [0] for creators/commenters/readers, it seems farfetched to suggest that reddit accounts (which benefits readers making an account to curate subreddit subscriptions) can't follow this pattern where many legitimate human users do not comment often.
Plenty of people don't comment often, but the impetus to sign up for an account is often to comment, which subs then either disallow or delete because they don't want new accounts commenting.