Treasure Never Lasts

All hail the Almighty Dollar (aka treasure.) Hail!

Hack & Slash has a lot to say On Treasure. I found the list of "Uses for Money" to be particularly interesting.

I like the thought of treasure being valued in gold, but actually composed of silver and other items.
What are the chances that you would just find a big pile of gold in a cave/dungeon somewhere?
Why did the denizens of the dungeon amass such a hoard? If they were going to spend it, wouldn't they be, ya know, out spending it? Do you have a big pile of cash just chilling in your basement? Unlikely.
Mostly you buy things with that money rather than just carrying cash around for the sole purpose of waving it in people's faces. You exhibit your wealth by the kinds of things you acquire, wear, ride, etc.

As a consumer, a good deal of what you spend your money on doesn't last. It serves an immediate need and then it's gone. This should hold true in gaming as well.
You dole out coins for a meal and a bunk at an inn. You pay for a cleric to heal your current wound. Maybe you buy a few potions to heal future wounds. Um...buy a few more. You are an adventurer, are you not?
You bribe an NPC for information. You give the smith coins to pound the dents out of your armor, or repair your broken blade. But you know it's just going to get dented and broken again. The cycle continues.

Consider this: spending money takes time, just as it does to acquire it. It's about supply and demand.

Now try thinking like, not just like an adventurer, but another adventurer. A competitor with minimal scruples. Why would you risk your neck to clear out a dungeon and rid the townsfolk of a local threat? There's got to be an easier way to "earn" some coin. So you hang around the tavern, scouting for jobs, getting the scoop on how much treasure is in the cave and what kind of threat stands in the way. You wait for some other party of suckers to go do the dirty work, then you nonchalantly tail them and wait. Just lurk near the entrance and rob the weary adventurers as they come out.
They're tired, beaten and bruised, they've probably exhausted their healing options, and their HP is probably looking a mite lessened. Now is the time to strike, you filthy opportunist!
You're deep in the back country. You have the upper hand. Take advantage. You could steal not only the loot they just recovered, but even rob them of their boots so they can't hurry back and tell on you. Yeah. You're a dick like that.

But you can't very well go back to that same town all rich and heroic like "Look at this treasure I recovered! Yeah. Me. That suspicious guy from the tavern that you didn't hire to do the job." Nope. You better make tracks and spend your hard-earned gold elsewhere. You're gone like donuts at a Weight Watchers meeting.

So there you are, laden with loot, and the itch to spend before all that silver burns a hole in your pocket.
Where do you go? The nearest brothel? Maybe a barber and bathhouse first? Then a fancy meal and a night on the town with several gorgeous concubines? Make it rain, yo!

Or let's say your DM is a jerk. He starts the session by saying "You've just cleared out the dungeon and have all this treasure. You're exhausted and can't wait to hit town for some R & R... But as you emerge into the sunlight you hear steel being drawn and greedy chuckling. '"You look tired." a deep voice says. "Why don't you let me and my crew carry all that treasure for you?" After you have handed over your hard fought spoils, perhaps after a thorough drubbing by the rival gang, they demand your boots, weapons, and food rations as well. They don't want you going anywhere anytime fast. You're penniless, unarmed, and barefoot with a long way to hexcrawl back to civilization. Let the adventure begin!"