Companies often have policies which favor type 1 errors at the cost of type 2 errors. That is, it is beneficial for the company to make the mistake of allowing someone to exploit them rather than make the mistake of denying someone with a legitimate (at least in the customer's mind) complaint. They have specific right off on their balance sheets that are basically "asshole costs."
If you go to any fast food restaurant, you can have them make you a shake, take a few sips of it, and then tell them it tastes wrong and have them make you another at no charge. In this way you can get more shake than you normally would. People can and do exploit this, but the vast majority do not. It's more profitable for the company to give out a free shake to a cheating customer than accidentally **** off a customer who legitimately doesn't like their shake.
When I worked at Hallmark during High school, I remember taking the craziest returns. Probably the best one was a used candle that we refunded at full cost (because according to the customer it didn't work anymore). The reason we did this is because as a card store selling emotional junk, business depended heavily on the mood of the customers. Especially at Christmas, little old ladies with nothing better to do would come into our store and buy literally thousands of dollars worth of collectible ornaments, most of which were repainted versions of last years. Keeping these crazy women happy was key to business, and so we'd gladly take a crazy lady's used candle back, not because it was the right thing to do, but because in allowing her to take advantage of us we got to take an even greater advantage of her.
The point here is that just because you can legally do something to a company doesn't automatically make it ok. They know you are a douche and taking advantage of them. They allow it because overall it benefits them, but you're still a douche.