Again; When someone breaks the rules, just delete the post.
The answer to this question is quite simple: because the community has quite forcefully asked moderation not to do this. Moderation started out by deleting posts and threads which violated the COC, but the community felt this approach to be too heavy-handed.
If a post was doxxing someone or making credible threats of violence or doxxing against another user, it would be deleted on sight. However, posts that call other users "cunts" for example are no longer deleted, though they do count against the posting user or users. Call-out threads are now locked when they are identified, so that they quickly fall out of the first page of any forum and so that they can no longer be used as spaces to actively bash others (in fact, the locking alternative to deletion was voted for in a user referendum held by moderation). However, moderation does not do deletion in most cases because it has tried to be responsive to the demands of other community members.
I'm inclined to believe they are worthless
If the individual in question was harassing you during the RO's active period, you needed to notify moderation so that we could enforce the RO. Moderation was not aware of any violation made against you during the RO period.
Most of these trolls probably don't care about temp bans or "restraining orders" when they still get to keep coming back and insulting the same users over and over again.
Unfortunately, that's probably true. That said, I don't think it is appropriate to leap straight to perm-banning "trolls." Everyone deserves chances to improve their conduct and reintegrate successfully into the site, and I think it would be adversely heavy-handed (and also perceived as overkill) to leap right in to perm-bans for "trolls." Bans, as they pile up on a recalcitrant individual, do escalate in length, but a perm-ban would require quite a few temp-bans leading up to it or an insanely severe act of misconduct such as doxxing another user. Doxxing is certainly one way to earn an instant perm-ban.