If they're anything like Starbucks then they get the benefit of utilizing the unredeemed balances as temporary capital for investments. It's an interest free loan at their scale. Plus they get to keep the balance that people forget to redeem.
I'm not an expert here, but this is not generally true. See "giftcard escheatment laws". I think these vary by state, but see e.g. https://legalclarity.org/when-do-gift-cards-become-subject-t... The value of abandoned cards goes to the state.
I am terrible at spending gift cards. I have some that are from 2007, 18 years old. Two years ago I decided I should check them all and actually spend them. Of the dozen or so cards (several of them for Apple), only 2 of them had an issue, all the others were still active with the original balance.
One of the issues was easily solved, it was a Visa gift card that had an expiration date... I reached out to the company and they issued a new card with an extended date. The other seemed to be so old that the underlying company was sold and pivoted, and changed systems (I assume multiple times) along the way. What was a card for a local restaurant chain now seemed dedicated to Dick's Sporting Goods... at least that's where the phone number went. I haven't yet tried going to the actual restaurant to see what happens.
This reminded me I did an awful job of actually spending them. I guess I need to try again.