Imo your "reputation" and general interaction across the forum is part of the access requirements. If you aren't active then how can people see that you will be around to handle any transactions/problems. Equally if you aren't "invested" in the forum then losing access isn't really a deterrent for bad MM behaviour
Equally, there are multiple posters with 5 figure post counts who I'd not trust to tie their own shoelaces. Being invested doesn't mean just posting to me; in fact I think you are overlooking a lot of invested people who don't feel the need to be argumentative or provide an opinion on every little thing. I've been around for 20 years (ish) and consider myself invested even if the post count says otherwise.