In an effort to prevent the misleading or deceptive promotional practices that can and has occurred in the Crypto Market App favorite Facebook has implemented a ban on any and all adds that involve Cryptocurrencies. Facebook understands that this ban is broad and intentional. The social network giant does claim to be looking toward revisiting this policy at a later date.
https://www.recode.net/2018/1/30/16950926/facebook-mark-zuckerberg-bans-crypto-advertising-bitcoin-james-altucher
I can see where a large company like Facebook is coming from, but there are far more legitimate ICO and valuable cryptocurrency out there than the minuscule scams. The truth is more likely that Facebook doesn't want to be associated with the bad publicity surrounding the crypto markets as of late.