Everything I have ever read about purse.io indicates that the gift cards there are purchased with stolen credit card details.

A lot of people use cash to buy giftcards, in order to pay for bitcoin anonymously. So now it's cash -> giftcard -> bitcoin -> giftcard -> physical thing. The future is odd.

purse.io is a money laundering operation for stolen credit card numbers. If it hasn't been shut down yet and its operators arrested, it will be soon.