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, based on what I have heard Facebook will not be allowed any digital currency ads on their platform. There are a group of people uses digital currency to scam other Facebook users. Bitcoin is not a scam, but it is on how was being introduced to other users. For example in the Philippines, there are a lot of Networking or MLM Scheme uses bitcoin as their main product to gather investment from other user and ended up as being scammed.
