It's interesting that in games with Looting, you just don't ever buy Gold.
Well, maybe sometimes there is no Loots left, or there are only Endless Chalices left.
Or Jeweled Egg is the only Loot-giver with no trashing (or poor trashing).
Or Search, but it's taking too long to empty a pile.
With Cutthroat, you may buy the odd Gold to activate the cards and get them back in your deck, if others aren't buying them for you.
And I'm sure there are other instances too. But these are just a few I found.