> We need to keep track of our customers’ account balances.
Right. That's what the blockchain is able to do. It can assert that you, who says you have 1 bitcoin in your wallet, actually really have 1 bitcoin in your wallet (assuming no attack vectors such as 51% attack).
> We need them to trust that their Wave balance is correct and Wave won’t lose the money.
This is the same argument as above.
> We need to comply with relevant regulations—know-your-customer laws, capitalization requirements, account limits, etc.
Not something cryptocurrencies have claimed they can solve.
> We need to provide an easy way for users to exchange their balance for cash and vice versa.
This is an implementation detail, and entirely depends on how the UX of the wallet is. Sure running a CLI tool and GUI that looks like it's from 2008 (at least it was last time I looked at bitcoin's GUI) isn't great UX, but you can build a different GUI for it. Something plenty of exchanges have already done.
> Of course, the above aren’t the main use cases of cryptocurrency today: those are speculation, theft, extortion, more theft, drugs, even more theft, and speeding up climate change. It remains to be seen whether legitimate, productive uses of cryptocurrency will ever justify the hype. We hope so!
There it is. This is just an article blindly bashing cryptocurrencies. I implore you to ask yourself, what has previously been used to do all the above? That's right. Fiat currencies such as the GBP, USD, and other currencies.
I may possibly be biased, because, I certainly believe cryptocurrency has its place, though I don't believe it will replace fiat. But this article is just unnecessary fear mongering with zero merit.