Usually it is just from me not taking the extra moment to uncheck the box when I apply some discretion to the move. I tend to do that more with the blatant spam posts.
However, users do complain when the move thread isn't there, assuming their post is deleted. Additionally, they can serve as reminders to users as examples of things that aren't allowed in the upper fora. Having said that, there are too many.
EDIT - A thought, maybe just leave them when they are moved to discussion fora, even the social ones. Don't have them for CN and AR. That would probably cut them down by 50-75 percent. I'll cleanup the upper fora.