Vber, whatsapp,skype are all social media platform, with an existing customer, and a service product with value, It is not all project/ Idea that need to conduct ICO, If there is a need for blockchain/ cryptocurrency development service that can be source for in the near future.
Facebook is a social media platform too but they are considering the initial coin offering for bigger funds. It's indeed helpful as what we have seen to the succession of the Telegram in which they raised more than a billion dollar. Perhaps the mentioned social media platforms are also considering it but as of now they aren't ready yet.