I understand everyones frustrations with annoying return policies. But, I can completely understand why stores require receipts now. In the end, it will benefit you.
I used to work at Ulta for many years. In the beginning they would allow any return of any item with or without a receipt. People would pick items off the shelves and then return them for either a gift card or cash if it was under $5. People also bought items at CVS for $2 and would return it to Ulta for $8. I had a woman come in about once a week with 10 completely used items and she would return them for store credit. So she would buy an item, finish it, bring back the bottle and return it for store credit. This happened for about 2 years. She got 2 years worth of makeup and hair products for free! All because the store was too nice in their return policy. The company was losing a lot of money that way which was effecting inventory, prices, wages, and hours.
Their policy now (as of a year ago) requires a receipt. You have 60 days to return anything bought in the store as long as you have a receipt. It can be used, broken, brand new, whatever, no questions asked. If you cannot find your receipt, corporate will search for the receipt for you. The stores themselves keep records for one weeks worth of transactions. I think that is a pretty lenient policy considering the amount of theft they had previously. After Ulta's new return policy, (I worked inventory so I saw the brunt of this) their prices started dropping. Also, their sales started to get really good. I know it is annoying to save receipts. But it truly does benefit you in the long run.
I don't understand why Old Navy gives out store credit for returns with original receipt. I'll have to keep that in mind the next time I shop there.