Action isn't taken on banning too often, this is due to the fact (in my view) that we really don't have enough mods to be policing every section-- though default trust painting the scammers red does pick up a lot of the work for the staff team here. So I don't see the lack of bans as an issue IMO.
The forum policy for dealing with scammers and spammers is different. As you can see yourself, a scammer or potential scammer would be tagged accordingly by DT. But that does not mean they are going to be banned.
In other words Red Trust and Ban are mutually inclusive and not exclusive in all cases. They may be exclusive if both offences of scamming and breaking rules are there.
Honestly I am myself often at awe of the huge amount of work the mods are having to do - to nurse the diarrhoea of the forum shitposters who are spamming the threads to get paid.