Their introduction is relatively recent. There was crypto before them. I use crypto in exchange for goods and services, not for fiat or a crypto copy of fiat.
Stablecoins appeared in 2014, including USDT. I personally don't consider that recent as 99% of the people who are in crypto nowadays didn't even know what crypto was back then. Of course, there was crypto before them, but its importance wasn't as it is today. In 2013 I can tell you I wasn't able to do almost anything with crypto besides buying and selling for fiat, all there was back then were faucets, gambling, silkroad, and maybe a couple of merchants that accepted BTC.
I'm glad you use crypto to purchase goods and services, but the fact crypto has gotten so big is because of stablecoins, which have allowed millions of people to trade cryptos for "fiat" in an unregulated and easy way. Sorry to break it to you but probably over 90% of people don't use crypto to exchange it for goods and services, they use it to make money, as an investment. So what's the easiest way to exit a position? Convert the asset into fiat or stablecoins. There is a reason 3 stablecoins make up as much volume as the rest of the market.
Don't get me wrong, the way you and I use crypto, in order to purchase goods and services is the whole objective of cryptos, but sadly cryptos have become an investment vehicle rather than a currency to be spent.
You do not know what you are talking about.
I think the one who doesn't know what they're talking about is you, but it's okay, you always have new things to learn.