Nice alternative uses, but fails in one point: they are adventurers, and if they want to adventure more, they’ll want to improve their adventuring skills.
That's what XP is for.
For example, my characters are the “save the world” kind of adventurers – even if the reasons are not totally “heroic” – and in order to better save the world, they need – or would greatly benefit from – good magical equipment.
In both our cases, making the world a better place is expensive.
Now, I think I wasn’t clear at that: It’s not that I don’t like the sort of game you’re proposing. I like it, and it should be supported by the system. However, I also like – and actually prefer – games with magic mart and such. The problem is (was, I’m not that interested in 5e now) my style isn’t supported. The guidelines (from what I remember) are too vague and just broad cost ranges are not enough.
I have magic marts my games to an extent. The market in town with the players are based occasionally gets in a magic item (ill make a couple of rolls on one of the lesser magic items subtitles to see what's in stock, and arbitrarily assign value based on the guidelines in the DMG. The PCs recently returned from 'the big city' where they were given an opportunity to make a few requests in a magic items shop (effectively it was a reward at mid-levels to ensure each of them had at least one magic items that they really really wanted). Made them pay for it and earn it though.
My PCs are also a notoriously drunken rabble rousing lot. They use carousing as their main downtime activity. The swashbuckler has been locked up a couple of times for drunk and disorderly, and our Druid (who has the bond 'I enjoy the finer things in life') is equally famous for her excessive gambling and drinking binges! Our LG cleric paladin tends to donate a fair bit of money to help orphans and the like, and to spread the word of his God.
Laughably, they still stay in the local tavern whenever they're in town and are yet to actually buy any real property. I might have one of the NPC make an offer to them to purchase a house in town when they get back from the current adventure. They found a pretty decent hoard with 40,000 gold pieces in it.
I remember back in the day my warlock PC buying a tower so that I could terrorise the local population from a base. Part of the fun back in the day was mapping out your own keep or tower, and stocking it with your own traps, mercenaries and minions.
Having a keep or a tower, your own henchmen or a subdued dragon as a mount and your own titles meant you 'made it'. You weren't just 'Grom the random murderhobo' anymore. Now you were 'Lord Grom, Dragon rider of the North, Conqueror of the Orcs of Malcozar, Warmaster of the Armies of Doom, and Lord of Aqualonia'
You didn't have guards dragging you before some Baron at the point of a crossbow forcing you to do some piddling quest because you're a troublemaker and an expendable asset .
Those same Barons would now travel to your keep and grovel and beg you for assistance saving the whole realm, because they and their armies can't deal with it alone.