Sorry, you're incorrect. The standard is absolutely 'is it useful for me to come here'. For me, at least. But there are lots of communities which don't meet the standard and I don't care what they do. If it fails the 'is it useful for me to come here' standard, then for all I care, the limit could be one panel per post, and nobody could have posted anything from that comic before. Or there could be a rule that you have to post porn with every post. Or 'praise only allowed, because we don't want Marvel or DC mad at us'. Any of the rules only matter to me so long as I'm here. Hell, the community could die entirely once it fails that standard, and although I'll feel sorry for those who continued to enjoy it, I won't really care about the event itself, because, to me, it died a long time ago when it became something entirely different from what I loved.
Now of course, you can rightly say that whether I'm here or not is of no concern to _you_, or to the community in general. But I tend to live my life on the theory that I'm not terribly unique. My views are probably shared by others. And if a change to the rules drives me away, it will likely also drive away others, or prevent others from joining who otherwise would have. I don't see a rule like the particular (utterly hypothetical) one I'm discussing specifically attracting anybody new to the community, so it strikes me as a net loss.