Earlier quoted context omitted.
I knew a guy who would buy three different kinds of a thing and return the two he didn't like... regularly. A small number of return abusers ruin things for everybody. Then again my last two online purchases, a pair of shoes arrived stained with somebody else's socks in the box and a cordless vacuum arrived with a mismatched brush head for a different model.
It's even worse than that, because they are adamant that they aren't abusing the system, and insist that if they didn't want people doing it, they would stop taking returns.
That kind of argument only works where stopping the behavior is cost free, the main reason most places didn't do it before was because the number of people doing it was low so the cost of actually tracking returns rigorously outweighed the benefit of low friction returns for the 99+% of customer who weren't abusing the system. When more people start creating large numbers of returns suddenly the amount of losses they create become enough to care about stopping. (Or it becomes a low hanging fruit to squeeze more profit out of an existing business, spending customer preference/loyality for profit by cutting a small waste center)