My issue with these kind of questions is that they're hardly ever done in good faith, and they show over and over again whenever crypto is brought up on HN.
Crypto has its good uses, and I've relied on it for my livelihood before (and even wished it wasn't just used as a speculation vehicle) when traditional banking couldn't meet my needs, so it's a very Americentric/Eurocentric thing to assume it's only ever good to speculate on and buy drugs on the Dark Web.
That's it- that's its killer app, it's an alternative to existing money transfer and store of value mechanisms, anything else like "smart contracts" or reduced carbon footprints from better Proof-of-Stake implementations are a nice bonus and worth developing, of course.