I'm going to make some gross generalisations here. If we say that an average gold piece is about the same size as a modern coin, that means a piece weighs 15g. A hundred coins weighs a kilo and a half. A thousand gold pieces weighs 15 kilos. Try putting that into your backpack. A large chest (1x0,25x0,25) full of scattered coins would contain about 150.000 coins. A sizeable fortune you can retire on. That also weighs about 2 tonnes and a quart.
The same values (1gp, 100gp, 100gp, 150000gp) expressed in gems and jewels:
1gp: a flawed semi-precious stone
100gp: a nice piece of jade, amber or amethyst
1000gp: an emerald or sapphire or two black pearls or ten pieces of jade
150000gp: 30 diamonds or exceptional emeralds or rubies
(figures roughly taken out of Pathfinder, I'm sure the editions differ on this)
What would you rather haul out of a dungeon, a chest weighing as much as a big car or a fistful of jewels?
One thing I like (in theory) about old-school dungeon raids and the gp=xp rule is that this treasure salvaging can become part of the strategic and logistical challenge. Part of the decision-making process as well as part of dungeon design. I rarely if ever see it being taken into consideration. The fact that encumbrance rules mostly suck is probably no small part of this.
Back to sensible things.