it could be that mi phones are so good that people like me and my wife do not want to buy a new replacement.
i dropped my mi 1S on hard ground one year ago. the screen glass was torn, but not detached; however, the touch is not affected at all. the face camera still works but the pic is blurry due to torn glasses covering the face camera.
last week my 4yo son threw my wife's mi 2. screen torn (much worse than mine, but the scars do not cross important areas like front camera), touch ok, camera ok.
i asked her if she wants a new phone? she flatly said no. it still works great.
i had a chinese no name brand tablet. dropped wooden toy on it, screen torn, touch broke, 'mouse' jitters. luckily pointers still functions with normal mouse (use utb-otg) after detaching the touch sensor ribbon cable.
so yeah, xiao mi phones are robust and ours are 24/7 abused. they (mi 1s and mi 2s) still get great build even when the prices are just around $100. the second thing less abused in my house is my lenovo yoga (ultra-slim laptop). oh wait, probably the most abused is my cisco router.
we do have more high end phones like motorolla and asus; however, they are not used as much as the mis. not because they are more expensive so we care more. it's just painful to use say asus. it's power hungry, and data hungry, often betrayed us on critical moments. we just don't use it. the asus z5 is now used by my 4yo son to watch youtube.
on last note, we like that our mis do not have a brand printed facing us, unlike the ASUS or SAMSUNG. i never like printed brand on my personal stuffs just to show off. printed brands on inside, not to show off, are ok.