Can someone explain to me like I’m a baby how why stablecoins are useful?

To add to this question, how does a company like CRCL make money off of "issuing" USDC. How does one just "issue" a coin. I get that you want a coin that is pegged to the dollar. But doesn't this defeat the purpose of wanting your assets tied to a currency that depreciates due to inflation (the dollar)?

I've heard when you buy crypto, you first buy a stable coin first. Maybe I don't see this buying through a broker like robinhood or coinbase, but when i buy BTC, I use cash dollars in my robinhood and/or coinbase account. What am I not getting here. Why tf would I want a stable coin?