Confirmation bias combined with the fact that unhappy people are more likely to leave “reviews”[a] (like here). I’ve never had an issue with Amazon that they haven’t resolved, and it may seem like I’m a minority, but Amazon is the size they are today because, for ever 1 fsck-up, there’s 99 others who didn’t have problems.[b]

[a]: Complaints. Reviews. Etc.

[b]: Not excusing their bad behavior. Just stating the reality.