Marketing
Apple are great at marketing, they take something that hasn't reached mass popularity and make it popular. How many non-geeks had heard of digital music before the iPod? Like it or not, 'iPod' is almost to 'Digitial Music Player' as 'Hoover' is to 'Vaccuum Cleaner'.
Looks how smart phones have really taken off since the iPhone, oh sure, blah blah, Android's better, whatever. My point is that people have a smartphone now that didn't before and they haven't even heard the term, nor do they care.
I think video calling could go the same way, it's been around for ages but it hasn't had good marketing behind it. Never mind whether it's useful, what's that got to do with selling anything? A great many people likely don't even realise that their phone can make video calls, that's not patronising, that's just recognising that some people just don't care about spec sheets.
I don't know if it'll take off and like it or not, neither do you. But you have to admit, whether you like their products or not, Apple are great at marketing. Even if they're selling only to fanbois they had to get those fanbois somehow and if, as the Apple-haters would have us believe, it's not on technical prowess it must be on the strength of their message.