Also, crypto currency is big market for the platform like Google because Crypto currency projects invest heavily on the ads and thus google benefit a lot from that.
facebook has already banned advertising of ICO's
not because the tech behind blockchain is bad. but because SCAMMERS who just act like script kiddies copy/pasting coins for a pump and dump scam..
google would go the same route at some point, because trying to vet these pump/dump ico's is next to impossible to guarantee that an ICO is sustainable and not just a pump and dump. thus the risks are too high
facebook didnt want the liability of suggesting that their customers should invest in such scams and so knowing the legal ramifications that people can blame facebook for suggesting they should invest outweigh's their income from advertising such scams.
so i can see google going the same route as facebook, just to legally protect themselves from lawsuits