Anyone who's ever upgraded an iOS device can readily see how well Apple thought out the process of transitioning the apps, media, settings, and data from one device to another. The ease of transition is just one point of stickiness that keeps users solidly in the iOS fold.
With an Apple product, you have multiple points of contact available -- most of which involve humans. Apple has their retail stores; and if you can't make it to an Apple Store but still want to talk to someone, Apple doesn't hide their phone numbers or try to steer you into automated Q&A queries. And they don't outsource their customer support to some boiler room in Bangalore.
Since Android is a common platform with multiple OEMs, and the most commonly used app services provided by Google and not the OEM, there are fewer points of contact that will keep customers loyal to one vendor over another. And the tactics used by OEMs to differentiate their products can have the effect of degrading the user experience. You're left with the choice of pure Android devices sold and serviced by Google, which has a spotty customer service record at best; or you take your chances with an Android OEM that might have a more extensive support network, but also loaded their devices down with crapware.
For all the criticisms of Apple as a secretive and arrogant company, they understand the human angle of the retail transaction AND aftersales support better than their competitors. What others view as a cost to cut, Apple views as an essential tool to gain and retain customers.