I can't really prove this but I'm pretty sure your ability to get a refund on Amazon is based on their scoring of you. If you're fairly large purchaser with infrequent returns they just approve your return no questions asked, but if you return a lot for your volume they put a lot of barriers in place.

At times it makes me wary of protecting my score (which may not even actually exist), and I'll often just take the loss rather than return something.