There is a reason stories often end when they do. You know the moment: the dragon is dead, the evil army defeated, and the heroes are standing in front of a giant pile of treasure that's bigger than any could hope to spend in ten life times. It's a happy ending. Other movies will gloss over what happens next. They'll just cut to months later, a year later, perhaps longer. You get to see how the riches have improved the plucky protagonist's life. But why skip it? After all, getting the treasure home can be an adventure in and of itself.
Money Has Weight
People often don't think about it but money has weight. This is more true the more 'historical' your setting is. How much weight? Well, certain denominations of cash have specific amounts to the pound and so drug cartels and other organizations that do a lot of cash exchanges will deal with money by weight. In the future credit sticks solve this for most people. But in the past where currency wasn't paper but coin?
In D&D 5e the system, as a blanket rule, states that a coin is .02 pounds of weight. That means 50 coins of any type is a pound. 500 gold coins is 10 pounds. 5000 is 100 pounds. 500 gold worth of value could be as little as one pound of platinum or 10 pounds of gold. Or it could be 100 pounds of silver. Or it could be 1000 pounds of copper.
This can get so ridiculous that if you're even paying attention to weight a little it's not unusual for D&D groups to just dump all the copper, and sometimes silver, just to make transporting easier.
How Much Can You Actually Carry?
A lot of times weight management and encumbrance gets thrown away because it's not fun. Sometimes this is done because - to be honest - most encumbrance systems aren't realistic at all and don't account for the distribution of weight making things feel lighter than perhaps they are. Still, even with that, how much can a person carry? How much can a man or woman with a maxed out strength carry?
What does that even look like? I mean, cartoons are fine with a strong man loaded down like a triple stacked wagon. But is that what you want in your game? And where does all that stuff go when the party gets into a fight?
A Self Made Escort Quest
I wouldn't recommend doing this all the time. But it can make for a fun "between" quest. How does the party get their hundreds if not thousands of pounds of loot back to their home base? The traditional way would be to load it into a wagon and bring it back along the roads. And yet, well, adventurers cut their teeth fighting the bandits that rob those caravans.
In effect, your party becomes a wandering raid encounter for bandits and other things on the road home. They get attacked, they defend their caravan. Maybe they lose some of their money. Maybe they don't. The point is, they get to see things from a different perspective.
Of course, if your party is prepared for this, let them have their easy trip. But if you need some filler, why not have the trip home be an adventure of its own?