> The problem with that is, when someone receives cash, they will often feel the responsible thing to do is save it.
That's not my experience of giving, receiving, or observing other people giving and receiving cash as a gift.
Most people seem (to me) to feel the responsible thing to do is to use the money in the way that the giver wanted for them.
Anecdote: My friend who was saving for a house received gift money from her grandparents. Despite the money being useful for her savings, she went and first bought a kayak with it, because that was more true to what her grandparents wanted.
If the giver says "please spend this on your hobby" then it seems to me that the money gets spent on that hobby - likely more effectively and perhaps more often than a gift card does.
Giving a gift card might force the issue, but that's not a good thing.
If someone needed that money to cover their rent this month, and is resultingly able to buy themselves something for themselves the next month, that's an awesomely good outcome. A gift card in that situation would be upsetting to the point of damaging.