At least one customer’s account was closed without a reason given until a customer service agent said the returns were the cause of the ban. Others revealed Amazon asked for reasons behind returns they’ve made despite providing a reason through the website previously. —Fortune, Lisa Marie Segarra
When working as an analyst with the Cabela’s Corporation I studied customer return trends. You know what I found? It is generally a small group of people who run the costs up for everyone else. This especially impacts companies who compete on price. One returned item may eat up the profit on the next 3 to 10 units sold. I've written about it here where it pertained to Apple. You’re never going to make your money back on these serial returners so it’s better to dump them. Walmart has already been doing this for years so Amazon certainly isn’t alone.
Even if a company has a no-questions-asked policy it’s because they’re estimating that most people are decent good people and won’t abuse the policy. If everyone turns into a serial returner I guarantee the policy will change.
Related: Stop Advertising Apple's Return Policy