It's baffling that gift cards are so popular. You're essentially paying to decrease the value of your own money by restricting its use and adding an expiration date (and handing to someone as a gift as if it's a thoughtful alternative to cash).
An even more egregious case is the corporate credit card. The company dictates its use exclusively for business expenses, yet pushes all the liability onto the employee. The business gets a massive, interest-free credit line with absolutely no risk. The company gets the float, and the employee gets the bill and the potential credit damage if anything goes wrong.
</rant>
Gift cards are great for companies you don't trust with (up-to-date) payment details. Amazon, Google, Apple, whatever evil megacorp you can think of, they all have made the news with stories like these, and they have proven time and again that they will stand by and defend their arbitrary decisions in court if they have to, because involving basic human intellect in the chain is too much of a fraud risk.
Even if you like their services, who knows what they'll do when they have access to your credit card information directly. I can completely understand why someone would pay for their services with gift cards bought from a well-known, respectable store instead.
It seems OP bought the gift card themselves as a means to top up their account balance (https://news.ycombinator.com/item?id=46252989). They basically used the gift card as an alternative payment option.
I still don't get why my friends and family think gifting a less liquid form of money is better than just giving cash.
Gift cards are the best proof against the existence of the homo economicus, that's for sure.