If Itch.io hides sensitive content labelled games on default then that means many users may never realize games are being hidden from them, especially if sensitive content labelled games do not appear for users that aren't logged in either.

This means that pornographic games which do have the sensitive content label will receive significantly less plays than those that do not have it, which rewards developers who either ignore or do not know the sensitive content label exists.

So the question is, do most pornographic games have this label enabled and receiving less views because of it is normal; or do most pornographic games not have this label enabled and those that do are punished with receiving less views. Since, unless games are actively being reported for not having the label, enabling it would exclusively be a disadvantage and jeopardizes the success of the game.

which rewards developers who either ignore or do not know the sensitive content label exists.

Well, they also risk having they project become unlisted, or worse … I don’t know specific details for Itch, but in general one doesn’t want to step over the rules of the platform that is hosting their projects, especially if that platform can survive without them.

Instead of trying to game the system, I’d suggest to focus on the intention of the rules. If your project contains adult content, then mark it with the sensitive content option.

There's no reason why NSFW projects would be overlooked by people who actually want to see them; that's what the checkbox in your account settings is for. And release announcements for example can be seen by anyone. That said, in my experience people seem to follow the rules and mark their projects as NSFW when they should, And that means developers, too, are responsible people who want to have the right audience. Hope this helps.