Just a small correction, if you don't mind. Admins/mods do moderate spam and they delete spam posts as soon as they get reported. But you are correct when it comes to scams. Scam posts do not get deleted and scammers do not get banned. Dealing with scammers is left to dt members and the trust system.
But shouldn't the admins/mods get in the way when it's definitely a verified scammer? I think that banning scammers would help a lot in discouraging that behavior in the forum plus it will be a war of attrition from then on between admins banning scammers and scammers getting craftier until they get tired of scamming, I do hope that the kind of system where every DT is in agreement that someone is a scammer and that they should get the ban hammer.