Amazon offers cash back for keeping your gift card topped up:
Amazon knows how to keep you topping up your gift card balance: offer a little money in return. It's introducing a Prime Reload perk that gives American shoppers 2 percent cash back whenever they reload their balance using a debit card. That's not a huge amount, but it could add up if you're a frequent Amazon shopper (rather likely if you pay for Prime). It's certainly your best option if you don't like the idea of signing up for a Prime Rewards Visa card just to get a return on your purchases.
It's not hard to see the incentive for Amazon, of course. In order to enjoy the savings, you have to pour funds into Amazon -- and that means committing to a purchase at some point down the line. You may be tempted to load more money than you need just to be sure you'll have something on hand, and that reduces the temptation to buy goods elsewhere.
Even so, this could do a lot to expand Amazon's audience. The company recently launched its Cash service to court people without any bank cards, and Reload appears to be a logical extension: it addresses those people who have a debit card, but can't (or just won't) use a credit card. In some cases, it could mean the difference between buying online and having to pay through the nose at retail.