Interesting thought. You are right, unlike casino gambling your return is never zero. Or is it?
With the rarity dispersion used can it be argued that “junk loot/cards” are tantamount to getting zero? I’d say so, but I’m not sure society has a consensus on this yet.
I think if the rarity curve were flat I might buy the “ you always get something so this isn’t gambling” a bit more, but the system is set up the make you “chase” rarer and more desirable items.
That said, I do think we need parental controls on this stuff no matter what, Kids are just way too susceptible to these sorts of manipulations.