Years ago I briefly played around with "manufactured spend" (on credit cards, to earn frequent flyer miles).
There was one specific loophole, with one specific gift card provider, and it was a doozy. You could earn credit card points on spend, plus supermarket loyalty points on spend, by buying gift cards from one specific provider which could be cashed out at face value (ie no fee at all) immediately to a specific type of savings account.
So, of course, world+dog was buying these things like it was the end of the world.
As I sat in a hotel room one evening rubbing the security codes off the latest batch of cards before redeeming them one-by-one into my savings account, it dawned on me that what I was doing was basically indistinguishable from money laundering. Of course it was NOT money laundering, but it would take some time to explain exactly why not...
The loophole was closed relatively quickly, and the gift card provider gave up.