It can also depend on the hardware it's connected to. If the endless gigabytes of Samsung's value-add software are scribbling to eMMC nonstop then it's not surprising the flash is wearing out. A lot of this stuff is masked by the fact that most people swap out their phone for a new one that's exactly the same every 12 months so they never notice this, but if you hold onto a phone or similar device for longer the unnecessary wear starts to add up.