"There's really no reason for crypto to exist"

There definitely are some reasons, precisely when reversibility works against you: eg. when bad authorities wrongly target you or censor you. Crytocurrencies give us payment networks that work even where traditional systems fail. No denied transactions. No limits. No "account" to open. Works for the underbanked. Send money truly anytime anywhere. No other system does this. That's the value.

It's absolutely possible that you personally have no reason to use crypto. But others don't have the same experience as you due to where they live, what political party they support, what they do, etc. There is a lot of censorship and oppression in the world.