There always will be certain percentage of people who will take advantage of return policies. I am sure at Amazon's scale, they can detect abusers easily. Most people hate to return stuff, and I think retailers take advantage of that, in general. That's why you see obvious lies in advertisements. Tesla's Autopilot mode? If society accepted returning defective or subpar products, then I doubt retailers will over-promise or sell subpar products.

Another option might be no returns at all. This way buyers will need to do their due diligence before buying and less likely to impulse purchase crap. Probably better for the society as a whole. Also things will be cheaper as retailers will not need to account for any returns.