build quality issues are not widespread to the whole android ecosystem. apple kind of get the crown as long term phones because software support and hardware warranties, but it's not as to say that there are no android phones that can match them in half life.
For those people, the alternative Android offerings just aren't on the radar.
On the other hand, the apple ecosystem doesn't have fire sales like Android does, getting last year's hip kick-started flagship got $200-300 isn't so bad, even if you need to do it way more often. See Amazon fire phone, nextbit Robin, essential phone; these were all a great value when they went on sale, although the fire phone has no back button, so it was more terrible than the others, but also cheaper.