The more the question is posed -- "Why is iOS dominant in comparison to Android?" -- the more I find myself irked. I know there is someone coming around the bend to bash one or the other, when they are both genuinely useful.
There is something to be had in either platform. There are positives and negatives to either platform. Whichever fits into your life at the time, you get it.
At least, that's what I think. I'm aware that the rest of the world isn't like me. But considering that I manage to make the best of whatever tool I have, I suppose I'm not really one to try to respond to this question.
iOS simply caters to one way of thinking and use; Android, something different altogether. I can do so much more to Android, and I can play around with Android so much more; that environment makes me think, explore, try new applications left and right. iOS, on the other hand, is about consistency; you find something you like, you find a work flow, and you appreciate that it doesn't change too terribly much.
Like I said, neither setup gets it perfect. For me, neither environment comes close to perfection whatsoever. I cursed my Android phone like I imagine I would an Android tablet, like I curse my Windows Phone device, like I curse my iOS devices, like I curse anything I use. I just don't see the point in trying to say that one is less curse-worthy than the other. So when Apple's commercials come on the television or pop up as "news", I watch them, chuckle, and move on; when I see people hugging iPads and iPhones, I know they are not aware of all the things possible with their devices. It's simply the culture we have in certain parts of the world that drive us to flock to Apple's land of technology, even though (in an ideal world) Android could be just as popular (and Android would be perceived to work with the same level of ease).