I think for me, boredom occurs because my phone is my most cherished tangible asset. If it wasn't, I would simply use it for what it is designed to do. Text, place calls, search the web, take pics, use apps, etc. For me, the iphone takes all of those things and does them each exceptionally well...
...But when it does not stop there, and your phone becomes an obsession of sorts, you start looking for additional ways to set it apart from any other device. Or perhaps anyone 'else's' device as well. You begin to seek out ways to make it look different, work differently, perform unique tasks, etc. Those characteristics give you conversation points, bragging points, etc. It becomes more than your phone. It is your show pony. Your extension of you. And when that happens, for me, boredom can set in because once I have mastered my device in every way, and run out of ways to tinker with it......I am then left to simply 'use it'. For those who are content with simply 'using' their device...the iphone is to me, unmatched. Because it works so damn well in so many ways. But for those who are not, or cannot, be content at that point....they jump ship to fill those other needs.
Android gives some remedy to those needs with the countless customization opportunities and lets face it, a new device of some sort every 3 months. But, once the headaches begin to outweigh that quench of the boredom thirst, and we are left wanting to simply 'use' a solid device again....we come home.
Not sure if even an ounce of that makes sense as it is hard for me to describe lol