There are so many factors. I had slightly bent my iPhone 5 in the past as I kept it in my jeans pocket. I'm 5'6", average weight and wear jeans that are snug (not tight). But when sitting with a phone in my front pocket, the jeans would put some pressure on the corners of the phone and over time, it bent slightly.
I won't keep my iPhone 6 in my jeans pocket as I can tell it would bend more easily due to larger size and thinner build. I bought a case with a belt clip... I put the phone in my pocket still, but clip it to the top of the pocket. So part of the phone sticks out and it does not bend. I've found this is the best solution for me.
Is this a flaw of the phone? No - it is just how it is built and I have to adapt to it. Anyone who thinks you can continue to put a thinner, larger item in something like a snug jeans pocket and not have it bend over time when you sit and apply pressure to it is not being realistic.
So just be intelligent with how you carry it around.