I just don't see this as true.
You make it sound as if gold is only used for your character, and it isn't. It is used for so much more. Here are just some examples:
- Gold can be used to curry favor from people in high places. Heck, to curry favor from a demon, devil, or arch angel, they might require 25,000 gold worth of (fill in the blank). I know very few groups that have that kind of gold.
- For the good group members, gold can be used to help out the town. They may be supporting the orphanage from which they grew up, the town or clan from which they came, or their parents and relative's farms. That might require a large amount of gold.
- I know you said most don't do the keep thing, but quite a few do. This is especially true for the character the character that is protecting something they have grown to care for: a town, a piece of nature, a portal to a place near or dear to their heart, or a portal to a very bad place they don't want reopened.
- Gold can be used for luxury living. If your group is tenth level and living in (fill in the blank big city), they want a very secure place for those magic items. They aren't going to trapse around with their special armor and 5,000 gold enchanted earrings and magic carpet each time they leave their place. So they will need a place that is safe, secure, and protected. That requires gold.
- Gold can be used for research. Go to Candlekeep to find (and need) a specific book; it's like going to Tiffany's and looking in their unique collector's case. This book might be needed for them to take the next step in their quest.
- Gold is often pooled as well. Sometimes, a single player in the group needs something specific for their build. And that something isn't always cheap. If you have a cooperative group, they will probably pitch in.
- Right now, my character's personality trait is: "I always have a plan for when things go wrong." He is a raging fighter that has come to look at the group as a family he never had. They are pretty high level (10), and have been near death quite a few times. Like real TPKs. He feels their luck can't last forever, so he has been acquiring and spending all the unused adventuring money on establishing a tavern as a business - so if he dies, they can stop this dangerous exploration stuff and retire to run a business. This has cost him a lot of money. (I write this to show how easily it is to establish this type of play into the game. Take a trait, flaw, bond, etc. and use it to establish part of the game. We have had several RP interactions based around that tavern: setting up a seafood vendor, getting the thieves' guild to deliver a piano, trying to get the deed, and hiring construction/artists to make it look how we wanted. All this RP was probably a drop in the bucket compared to play time, but it helped the economy of the game and flesh out some of our characters.)
- Gold can buy potions to help the group. Heck, we just paid 500 gold for a potion of resist elements. 500 gold! That was a third of one character's net worth!
No offense, but this list could go on and on. So, it feels disingenuous to keep complaining with all the suggestions people have given. It is a problem that clearly can be solved. And not only solved, but seamlessly worked into the game's RP, exploration, and combat pillars. The fact that your table can't seem to accomplish it says more about your playstyle, and not so much about the game.
One last suggestion: If your playstyle doesn't match the gold/economy, just limit the gold. That's it. Cut all gold your group gets in half or quarters.