The statistics sounds BS (as a lot of them are).

FWIW, I don't know anyone (across 5 countries of friends and business partners) who doesn't use Skype.

Skype's use prevails mostly around international calling, video conferencing and professional chats. It isn't really an everyday use thing like WhatsApp which, where dominating, is an entire replacement of SMS. My Skype account gets sparingly used for anything else than talking to a client.

That could make sense, because that's what I've seen it used for: international calling, video conferencing and professional chats.

Still, wouldn't that amount to more than 30M users?

Only?