I honestly don't know why people let prepaid gift cards (especially those by VISA, MC, and AMEX which can be used anywhere they are accepted) expire.
Just think of them as [insert value of gift card] off coupons. If you received a $50 VISA gift card, think of it as a $50 off coupon that can be used almost anywhere you can use a VISA card. Is it that hard to use a VISA gift card for gas or to pay off some utility bill or something?