In Canada gift cards cannot expire, and you don't need to provide any personal information -- you just buy it at the supermarket or where ever. VISA/AMEX gift cards are the only ones with extra fees attached and I avoid those like the plague.
Your mileage may vary in other regions. I've never heard of the interest one (hang on, they're already holding the money - shall they pay me the interest?) and I don't think the cards in Australia have personal information attached - they have a PIN which is printed on the back of the card.
Many in Australia work in multiple stores, too.
Expiry is the real bug bear, and probably the best reason for the cards to be offered. I'm sure the percentage of cards that are never redeemed make it all worthwhile.
But if you want your gift to be at least one step away from cash, then that is the price you pay. ;-)