Timothy B. Lee at Forbes, “Why Google Is Winning the Smartphone Wars”:
This explains why iOS has been losing ground to Android even though most people agree that the iPhone is the best single smartphone on the market. There are tens of millions of people who care most about the narrow end of the funnel. They want the best user interface, and are willing to make compromises on other fronts to get it. Most of these customers will opt for an iPhone. But there are hundreds of millions of customers who care more about some other factor. They want a phone from their favorite carrier, a phone with a physical keyboard or a removable battery, a phone with their choice of app store, a phone they can get for free with a contract, a phone they can get with a pre-paid plan, etc. No single phone (wireless carrier, hardware manufacturer, etc) can satisfy all of these diverse customers. Only a platform designed to support many different phones from many different manufacturers on many different networks can cope with this kind of diversity.