Samsung also makes a hundred phones, half of which are given away for free. I'd wager that most of the Samsung phones are sold to people who don't realize or don't care what brand of phone they're getting.
The thing about the iPhone is, you walk into a store and you ask for it. When I bought my 4, I had to threaten the salesperson after he twice informed me that I didn't really want an iPhone and would do better with some HTC. It's all the more remarkable that Apple does as well as it does given that carrier saleschimps are operating on orders to steer people away from the iPhone because carriers make less money on those handsets than one Android phones.
tldr: People who know what they want buy iPhones. People who don't know end up with Android.