In many cultural circles it’s very rude to gift money (or to even left the gifted know how much something cost).
Giftcards are seen as a way around that (although they’re not really better). They also show that you thought about the gifted (what would this person like), but respect that they might not like the specific gift you’d pick.
e.g. if you know someone is a LEGO collector, you gift them a LEGO gift card, instead of buying a specific collectors model that they might already have.
I understand a non gift card gift conveying that someone thought about the gift recipient and/or is not explicit in its cost, but a gift card accomplishes the former poorly, and the latter not at all.
I don't get it either, but people do use them that way. Some are even sillier: a friend of mine, who teaches classes to seniors, got a gift card from them that can be spent on any shop of our huge local mall.
Giftcards are seen as a way around that (although they’re not really better). They also show that you thought about the gifted (what would this person like), but respect that they might not like the specific gift you’d pick.
e.g. if you know someone is a LEGO collector, you gift them a LEGO gift card, instead of buying a specific collectors model that they might already have.