People used currencies before the existence of central banks. They used gold, silver, etc. We don't need central banks, they are a cancer that create inequalities and inflation. The fact that securing a decentralized proof-of-work network requires energy doesn't mean that it's a waste. You can also buy food, housing and clothing with cryptocurrencies.

El Salvador keeps buying more Bitcoin and lots of people keep using it as a currency there.

Well it isn’t protected from rapid deflation.

Bitcoin is deflationary by design, but that's an advantage, not a problem. It's like saying that gold is bad, because it's worth more and more every year.

all the advertisements presenting it as an “investment”

It has been one of the best returning investments since its birth. Even Black Rock and many other companies consider it as a great investment.

Also, I’m not sure who needs to move large quantities of money across the globe. I just want to exchange money for his it services.

Believe it or not, there are rich people who need to move large quantities of money to buy houses, to buy land, etc. You can also buy small things with Bitcoin, of course.

You can use Bitcoin to buy food and small things as well. No, actually scammers and criminals are among the minority of people that use Bitcoin. Many people use Bitcoin for their daily needs.

It’s a hassel to move large amounts of money from one country to another because the stakes are so high and everyone involved wants to make sure it is done properly.

Stakes are high? I don't think so. The problem is politicians, the hundreds of worthless currencies that exists and the expensive banking cartel with its high fees. People should have the freedom to move their money as they wish, because it's their money.

You can actually buy houses using Bitcoin, I don't understand why you wouldn't do that.

It allows sending value anywhere anytime and it protects you against inflation, because it can't be debased. You can also move large quantities of money without needing permission from anyone, anytime you want.

On the other hand, fiat money creates inflation and is controlled by central banks.

It won't crash to zero as long as there is a computer mining that supports the network. Normies that talk about the environmental impacts of cryptocurrencies don't understand.

How many wars were created over fiat currencies and the power plays of politicians and central bankers?

Fiat currencies are inflationary, so they encourage economic growth (at what cost? At whose expense?). That inflation also attenuates the indebtedness of states, it is like an invisible tax against the poor and the financially uneducated.

There are cryptocurrencies that are trash, that don't provide privacy, etc., but you can't tar everything with the same brush. Moreover, the environmental impact is minimal compared to fiat currencies. There are cryptocurrencies that pollute more than others, of course. For those who care more about the environment, there are cryptocurrencies that do not use proof-of-work algorithms.