Pretty much this.
We had talked years ago about banning people from specific sections of the site. Example: consistently don't tag/repeatedly upload NC stuff/upload everything to tumblr despite multiple warnings/suspensions: banned from uploading images. Frequently abuse the Serious Debate board by shitposting: banned from Serious debate.
However, while this may seem like a good idea (and personally I'm not inherently opposed to it) what would it really accomplish? We make a special feature for users that lack self control to stop them from getting themselves banned for misbehaving? If users really want to improve, they will head the warnings and suspensions and change their behavior. If people want to go out of their way to get themselves banned, that's their business.
Again, the notion I don't really think is a bad idea, but it would take effort for James to make it. Effort that could be going towards better things. Between holding the hands of users who lack self control and would probably end up banned anyways, and getting features that would actually be useful for the user base at large, I can't really say that it's a feature we really need.