There is always someone willing to abuse the system no matter which system it is. I was in Costco one day a few years back waiting to renew my membership and in this store that line is next to the return line. A guy in the return line had what looked like a 10 year old printer he was trying to return. No cords, no software, no box and of course no receipt. The return clerk was saying Costco never sold that printer and this moron is insisting he did. Naturally he had kids with him teaching them honesty and integrity. I don't know what the outcome was they were still discussing the situation when I was done but no wonder Costco changed it's return policy.
Companies must be aware of the abuse and find some level where the losses from abuse and customer considerations balance. Some, like Costco, seem to find a reasonable balance.