I don't think you're giving the argument enough credit. Nobody says "I got my iPhone repaired cheaply and now the touch isn't responsive"; they tell their friends "God my iPhone sucks these days".

It's the same reason Kleenex sues when people use their brand for generic products, or Disney forces daycares to take down murals of Mickey, or Burberry burns unsold products. It's a slipper slope away from quality, and while no one thing is a huge deal, the culmination is.

I agree at the end of the day it's about making money, but that's just what being a business is. For certain brands, they want their products to be meticulous. It's not the only way to build a product (see Android), however it is the reason Apple products are so beloved by the people who buy them.