The last social media "platform" I have heavily used (ignoring HN) was MSN Messenger. Reddit/Twitter/FB/etc. never got my attention somehow, but now I see more

The last social media "platform" I have heavily used (ignoring HN) was MSN Messenger. Reddit/Twitter/FB/etc. never got my attention somehow, but now I see more and more people leaving them. I guess that must be good. I still don't understand why WhatsApp (and similars) requires a phone number (from a technical point of view). If someone releases MSN Messenger with a modern UI/UX, I'm in!