It comes down to the usefulness of cryptocurrency. Why use Ethereum or Bitcoin instead of plain old cash? And this usefulness has to be apparent to the masses. Personally, I can't think of many reasons besides it being decentralized. So I would probably say it is a bubble, way overvalued.
Fast transfer of money with low or no fees, actually owning your money so that a government or bank can't freeze your account for different reasons. programing your money to do something or go to someone once terms are met through smart contracts on Ethereum, eliminating the trust you have to rely on at the moment with contracts in the real world. You could program your money to be sent to a specific account of your choosing once you die ( if you stop updating the contract once a year for example) instead of making a will and having people fight for what they should get and have people sue each other... Having the information of property on a blockchain, or ownership of your car, decentralised voting systems that cannot be rigged by third parties....Hundreds of use cases, can't list everything here...
Also, you can memorise a string of 20 words and have billions of dollars stored in your brain that no one can access or take away like when paypal froze wikileaks account because they can...
Oh, and I forgot, Cash is monopoly money backed by debt to the banks that print as much as they want
Huh. I will admit I don't know a whole lot about it, but thanks for enlightening me.