I can't say I actually know anyone who uses it, is there a use case I don't yet know about?
As far as I can tell, it's useless tech for the sake of tech.
All other monies leak value fundamentally (through increasing supply or maintenance costs or risk or lack of liquidity etc.) whereas bitcoin's supply is hard limited by mathematics/logic, there's no maintenance costs, there's almost no risk (once you understand it) and I can exchange it directly with anyone, 24hrs, 365 days/year for hardly any cost (remember that the base layer network is optimised for large amounts of value)
It's money boiled down to it's purest, most ideal form, but to appreciate that takes 1000hrs of hours of learning both what money is, and how bitcoin works. Few people know either one, and far fewer both.
It is a fantastic use case because now you can borrow up to your collateralized limit, without talking to anyone. Thus enabling you to make pet rocks work for you.
DeFi really is a great usecase. It is of course, early days, meaning that it can be high risk, but it can also be high reward.
Lastly, this is one of my favorite comments here on the subject of usecases: https://news.ycombinator.com/item?id=26238410
With an offshoot BPO wing, they've recently moved to claiming, via press releases, their entire HR function of 60 people has been reduced to just 2 and AI. Which I find hard to believe as I'm still in contact with 10+ of the HR doing the exact same jobs with the exact same broken spreadsheet workflow they always did.
1) intelligence agencies
2) child pornographers
3) ransomware operators