It's a marketing tactic to make things more complicated than they need to be so you just throw up your hands and buy based on gut feelings, ignorant of the true facts because it's just too hard for average consumer to do the hard work.
I think it's really sneaky when I'm in Target and see that the 8 or 12 pack of paper towels both cost more per roll than the 6 pack. It's like they are using predatory pricing to take advantage of people who assume that buying in bulk saves money, so anyone without a calculator would lose money.
I can see how OEM computer parts would be under similar marketing pressure/tricks to use rebadging for mass-market customers, unlike the specialty enthusiast market where we all do our homework.