Facebook grow up so huge, it is too big to adjust fast, and implement quick very important changes (blockchain technology for example) without dividing its member. Also FB relies a lot on the elderly audience, talking about 30-60 year olds. Those who are <30s they can still learn, adapt, or be capable to learn new crypto movement. Imagine your grandma, which is on facebook trying to teach about blochckain, about Segwits, about crypto etc etc.

Just the actual move of banning the ICOs adds, is the odd one, when M.Zuckerberk mentioned about FB possible blockchain implementation, or even their own crypto coin creation.

As a business person I can tell one thing.... FB has very powerful shareholders, and the only weakness FB has is problem with ROI, when the social network has so many users, and the earnings are so little. This is how shareholders see the whole situation. So maybe this ban of ICOs, or other crypto ads, is the first step into their own crytpo creation....

...well good luck!