I can certainly recognize the scammers but I guess it just isn't worth prosecuting. It is so transparent that it is rather humorous.
That said, my last RV sale, the buyer gave me 2K in cash and 4K in a bank (cashiers) check. After getting the trailer home, he decided it needed more work than he initially thought and put a 'stop payment' on the bank check. I didn't know you could do this but that is what he did and my (ex) credit union deducted from my account and sent the money back. So he had my money, my trailer and my title. It took one call telling him he purchase as-is, with the ability to have the trailer checked out which he didn't do, and he decided it was better to go to his bank and wire the money to me.
Having a lien seems to be a bit of a safety net as they are responsible for seeing that the money goes through correctly. Interestingly, when I bought this MoHo, we were both using the same finance company and the company waited 10 days for their own check to clear. Go figure.