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.
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.