I don't use Facebook but for example KLM/AF at least 5-6 years ago pushed hard "means of contact" as "talk to us at whatsapp/facebook". And they weren't the only one. And the track of thinking was probably "If everyone/millions use it then let's move away from this old pesky email"...

There are groups/communities (real ones, for example building or school) that settled on WA/FB group so while you are not necessarily forced to if you don't there is a high chance that you will miss some crucial info…

I don't use it in any manner for personal communication though…