See, if I've paid $200-$400 for a used or refurbished laptop that has issues, I can either sell it or replace part of it pretty cheaply. No big deal, and worst case I'm out a few hundred dollars. If it's a full price new laptop and I can't return it and can't sell it for full price, now I'm out potentially thousands of dollars.
I end up using a lot of zombie laptops. I'm typing this on a Latitude 5410 keyboard/bottom with a Latitude 5400 display and back (the connections/hinges are compatible).