My experience has been a little better . If people spend money on them, the chances are better they will get redeemed. My previous company sold a large sum in gift certificates each year, redeemable for a specific picture package at one of the children portrait studios I owned in various states. Our redemption rate was around 80%, but we also requested an email address of who the certificate was given to and if it wasn't redeemed within 60 days occasional email would go and and remind them to use it before it "expired" and right before they expired a reminder email would go out, telling them to hurry and even offering them a little "bonus" if they came in within a couple of days.
We also gave away certificates for various contests through the years, and those were still redeemed at a decent rate, but if I recall it was more in the 40-50% range.
currently I give free Kodak metallic prints and gallery wraps to winners of various contests at my store as well as places like the local camera club, and most of those are redeemed.
The recipient has to appreciate the value and the product being offered. They usually don't have any skin in the game since it was a gift and if it isn't something they are interested in they most likely will file it away and forget about it.