I'm a little lost here. Why is Skype popular? Doesn't FaceTime do the same thing (video calls)? And, if I already have an iPhone in my backpack why do I need another app to take calls?
Maybe for people that have "only use apple devices" as a requisite to befriend someone. For the rest of the world, no.
p.s., Skype is more than videocall, and videocall is silly anyway (for most purposes). After all, theres a reason why videocalls flopped like a decade ago (and no, it wasnt because Apple wasnt around). The only people that seem to truly take advantage of the technology are deaf people, but for them, videocall is about as revolutionizing as the phone was for us - so no wonder.