Cold hard cash, so often the reward for a fight in D&D. Never mind the dodgy magic item economy that’s designed to follow this scooping up of coinage, let’s consider the practicalities.
Have you ever counted out and stacked one hundred coins? What about a thousand? Ten thousand? I have. It’s mind numbing. And that’s with modern stackable currency almost designed to sit right. You can get little machines designed to weigh money bags, but that also relies on modern minting consistency. I shudder to think just how long it would take to even remotely accurately count out coin based loot in a dark wet monster infested dungeon.
And then you have to carry it. Know what it’s like when you’ve somehow ended up with more than ten pound coins in your pocket? It’s like having a small rodent squirming around in there. You’re almost desperate to find a car park so you can offload the chump change. Just how much would 100gp weigh? (I could look it up. I won’t though.)
Point being: I love imagining the tiny dark parts of D&D. I couldn’t give a monkeys about Gate spells or Crafting potions (which fill entire sourcebooks with their explanations and expansions), but I do love thinking about the grubby business of spiking doors, spilling oil, and counting coin.