google ha many reason to ban this adds because it is very difficult to determine which ones a legit and which ones are scams, so they don´t want trouble and get out of it.
Because google always protect their reputation. They don't allowed deceptive controversial ads.and to protect the scammers to enter their sites. Because a lot of ICOs now are scammers and fishing sites. I think google want to settle this issues.They want to eliminate this scammers in crypto.