If gold equaled XP, most merchants would be demigods. Now, for my campaign, some of the merchants *are* near demigods. But, the characters are 20th level with epic boons and are exarchs and such. One such merchant is Wal'gren, a mercane that specializes in enchanting with residuum baths and improving items. If you have the wealth of a nation and want a god-weapon or armor special done, he's the one you see in Union to have this enchanted. He has customers from around the multiverse.
But, I doubt the largest major city grocer is epic level though they sell enough food to supply a city and pay nice livelihoods to everyone from workers, managers, artisan cheese makers, animal breeders, butchers, wine makers, etc!
I do not think either me or the other DM at the time used gold = XP in our campaigns in the 2e days. Then again in the 2e days, there was so much homeberew you could go from one game to another and it be vastly different.
I like some other systems and have dabbled in some of them in the past. Most of them were one shots or something I ran into at a convention. Some of them I like, others I can take or leave.
Problem is in marketing and recruiting for players when that comes up. The words "Dungeons and Dragons" is the milkshake that brings all the people to the yard. If you start deviating from that too much, you end up with your own system which is less marketable. Most of the prospective players have heard of DnD. Some may watch Critical Role or played DnD when much younger. DnD has become ubiquitous. You deviate too much, you lose that draw.
I remember one time years back (2004), I found myself in need of a game. Turnover, people moving, and World of Warcraft decimated my gamer pool. I wanted DnD. I went to a local meetup designated for people to meet other gamers. Problem? No real games. There was one guy there that the organizer whispered to me had lost 2 groups in a row because while he "played" DnD, the real game was some kind of custom power fantasy ego deal with powerful DMPCs and custom rules that changed on a whim with him and his girlfriend being all powerful. Nope. The other possible game was one of these aspiring game designers trying to playtest some custom game to publish. More power to him, but was not something I wanted to get into at the time.
No one got gamers that day. (Organizer had 2 or 3 full groups and merely facilitated the meetings. Bummer. i wanted on with them!)
But.. If someone ran DnD... real DnD even with a lot of house rules mixing in some things, the people would have come.
Which is exactly what I did. Organized it myself. Had plenty of games. But I doubt I would have done it if it was not DnD.