Banning accounts of such scammers is going to put so much burden on the shoulders of the admins/moderators and even with bans they can still create new accounts and find ways to continue their old habits. Although, you're also right that they may need to buy copper membership to embed images in the posts but still that won't help the forum in any positive way.
It will be more easier to deal with a newbie account that was created for the purpose of continuing an act that resulted in the ban of their previous account than a high ranked user on the forum even with their tag if they are not banned. If they should decide to buy a copper membership account so they can embed images then it will obviously be their loss because the account will eventually get tagged as well thereby losing its reputation.