> When I buy a pack of tokens rather than depositing USD or similar into an account, I'm more likely to spend all of those tokens.

In my experience, it's exactly the opposite, since packs of points/tokens are not typically divisible by the price of common purchases. For example, you might have the option to buy 500, 1500, or 3000 points; items then cost something like 740 or 800 or 1600 points. To spend your last point/token you almost certainly have to buy more than you originally intended.