Since popular social media networks like Reddit accept Bitcoin as trusted method of payment for their marketing services, to ban cryptocurrency ads on FB is quite a strange idea. Anyway, I cannot understand why they are so picky, when FB, the social media giant, has become an advertising network more than a social one.
In my opinion, FB is used more for marketing purposes than personal use. This segment of audience has migrated slowly, slowly to Instagram and other networks. So, taking a decision like this - to ban an advertising market like crypto on FB - doesn't seem to be the best for them.