There’s just too many poor ICOs launching and floating around for Google to moderate and police all the potential ads they’d buy. Google has shown no issue with deliberately reducing the service of it’s product to offset future headaches before.

> They just don't want to be associated with companies that are related to fraud.

More specifically, Google doesn't want the SEC to hold them liable when they go after some of these fraudsters.

They also don't want:

* sites abandoning adsense because they don't want to be associated with cryptocurrency

* users installing adblockers because they don't want to be running monero miners