The scams are a risk for some lawyer in some country suing YouTube. They bring in a lot of money now so YouTube is not interesting in policing them, but they are a risk that they will suddenly go away for legal reasons. which is why I don't understand why YouTube doesn't police them now - between the potential loss in court and the big companies staying away there is a lot of risk to YouTube.

Note too that if YouTube would police scam ads better they would have a better message to various countries that laws and legal action is not needed at all. Right now I'm shocked the EU hasn't put in place harsh laws about ads - if YouTube would police their own ads they could have a slightly less harsh policy in place and thus make it not worth while for the EU to pass the harsh law they don't like.