- the possibility to hide some transactions out of the traditional system (monero / zcash). I mean you may disagree, it's mostly ideological for some honest people and practical to some dishonest / drug dealers / evaders.
- the fact they are decentralised currencies that are now an actual alternative to people's national currency. this may look silly to you if you live in europe / usa, but a LOT of less developed countries such as lebanon, turkey, and a lot in south america and africa have seen the value of their currency decrease steadily wrt the dollar. So ANY of this people would have been better of buying either dollars (which may be hard locally / with taxes), and even better off any crypto in the past 10 years instead and they would have better life savings.
tlrd The biggest value of bitcoin now is to be alternative store of value, which you can acess pretty much anywhere in the world in a decentralised fashion. Even if the tech were useless, its DE FACTO an alternative now which doesn't have less value that 80% of local / national currencies.