Orkhepaj: it is backed up by the tax and trade system
Lesser: Todays money isn't backed up at all. Even if people just would turn their bank account money to notes and coins there wouldn't be enough - Greek is the best example years ago. The old concept was that one Dollar was 1/x of the available gold. We just traded with some kind of stocks. Today we
need to trust we still will be able to recieve that gold - if people would do that with enough money, sooner or later those people cannot get more because everything has been traded.
aCyborg is completely right: money itself has no value. Money exist because we trust in the system that we can get everything we need with that. In Turkey it is better to have your money in Dollars instead of Lira at the moment. When Germany was divided, there were special markets called "Intershop" where you could buy exclusive goodst - but you had to pay with the West Germany currency, they didn't accept the East German currency.
Gold is similar to money anyway. Even if all the money is still backed up, who really needs gold? The practical use of gold is non-existant for common people: you can't eat it, you can't really build something with that like a house. It is just shiny, a rare resource and it is useful for cables.
If enough people trust Monopoly money, you could even use that instead. That's also how Cryptocurrency works.
Edit: back to NFTs: If Ubisoft wants to do this they could start converting our games to that system. Yeah, I could trade some skins but why stop there? Let's trade the whole game like back in the days when games weren't bound on accounts but retail boxes where the biggest pain was some intrusive copy protection like TAGES and Securom - at least you were able to give that to someone else. No? Would that hurt your company? Aww....
Unfortunately true. Actually bank notes from since when they were first introduced to now (uk anyways) has the words, “I promise to pay the bearer on demand the sum of xyz”. This was then backed up by the Bank of England holding funds in terms of gold and other precious metals/commodities, but also revenue, e.g. economy. However this changed back in the 80s with a big government change in focus, from pushing for things like saving to spending, earning to credit, work to welfare. Now the whole system only functions due to momentum. Things like covid could theoretically bring the whole thing down. Although it’s unlikely as markets can rapidly change now due to other markets and economies buying/selling debt.
The real difference is current currency is a huge globe spanning ancient beast which is very robust even if it does not look like it, and has a lot of trust and backing. Bitcoin, nft’s etc. have none of this, some d-head in Silicon Valley thinks it’s a good idea and bam it’s everywhere, going up down, everyone scrambling to make or lose a fortune. It’s merely an extension of the gambling which is on the rise everywhere.