Their reputation is probably the biggest reason.
If I buy something that has a real standout defect, especially if it doesn't show sign of improving, I'm not going to buy it.
It's like restaurant reviews. Most people likely won't be vocal about a good or mediocre experience but from what I've seen they will comment about a negative one.
For example if I bought a Switch Lite and was stuck with joycon drift you bet I'd tell someone who was looking for a Switch.