This is all due to fraudulent ICOs. At current time 9 out of 10 ICOs are total scam. They do a fundraising and spend nothing on anything except for roaming around and spending in useless things. And it's a good move from social sites to block those ads until we have regulations of the ICOs.
While I agree with this, I hope that Facebook, Twitter, and Google, all reverse these policies once we have some decent regulating bodies in place that can actually prevent all the fraudulent bullshit going on right now. The combination of those scams plus the bans is just a massive blow to the industry and we are all feeling the pain very heavily.