Because they believe that Facebook prohibits bitcoin and ICos and other cryptocurrency
The new Facebook policy will not allow announcements of known digital currency exchanges or initial offers of currencies.
Is it to avoid fraud or false advertising? That's why?
yes, facebook does not really against bitcoin, they just wanted to avoid the advertisement that happens in their website before which is even the scam ico's will get advertise, so the possible thing is, some people might think it is legit but it may not