Today, we just had two cases on this site where a tag had been removed from all questions, but was used by a new user in the meantime while it hadn't been removed from the system yet.
The tag confused-users had had a burninate request filed for it earlier this month, and had been approved by a moderator the same day. Yesterday, we removed it from all questions, or so we thought. Four hours after it was cleaned, it was used by a new user in a new question. When we attempted to remove the tag, the user continued to edit war for its inclusion, even after being told two times that the tag was in the process of removal. This new use of this tag ended up delaying its complete removal from the system, which deletes zero-use tags with a script that runs every 24 hours. That question got locked as a content dispute.
I thought that that was a one-off, the end of it, a rare case. But just half an hour ago, the exact same tag was used again by another user, who also continues to war in including the tag, threatening to delay its purging again, increasing the time this situation could potentially happen for the third time.
None of the above would have happened if new users without enough reputation to create tags would have been blocked from using tags that had zero uses but hadn't been purged yet.
This is already blocked in one case, in suggested edits. This request is to also block it in other cases, i.e. binding edits to own questions and community wiki questions, and in newly-asked questions.