Their reasons might be valid in banning somecrypto ads. Google, Facebook and Twitter just want to protect their users from possible scams from crypto and ICO related ads. The google ban is for any kind of ads related to cryptocurrencies and related contents will no longer be allowed in Google's AdWords platform. But some argued that there may be a bigger issue at play and not just the reason of protecting their consumers or users. Whatever the outcome of this restrictions, i'm hoping that it would not affect cryptocurrencies in the future.