It's only relatively recently in the history of commerce that assets and currencies have been truly disconnected. The Gold Standard ended in 1971. However, the Gold Standard was based around a stated value of gold, which does not align with the crypto market.
Cryptocurrency (in general, as a whole) is a poor currency because its intrinsic value is unknown. Nobody knows how much a BTC is worth, unless they align the BTC value to the value of a fiat currency. But that fluctuates so much, it's not possible to implement a BTC-based commerce system because the value of a currency needs to stay reasonably consistent across the lifetime of the commercial transaction. We've seen repeated examples of what happens when the value of money changes between the money being issued to a citizen and that citizen spending it: usually this is just a few percent in the form of inflation, but we've seen enough examples of the destructive effect of hyperinflation through history to know that rapid value changes are a bad thing.
Also, cryptocurrency isn't really an asset as you can't do anything with it except carry out other financial operations. In this way, most cryptocurrency's similarity to assets is the same as my jar of coins: it's a store of some value to be exchanged later for goods or services. Some cryptocurrencies have been created with the intent of underpinning the management or ownership of assets (e.g. Ravencoin), but these seem to be a "solution looking for a problem" rather than a viable investment opportunity right now.
For me, the biggest failing with crypto right now is that there isn't the right level of credible confidence in it. The discussion around crypto is all amplifying: whenever crypto is up you get all the believers shouting about how great it is; when it is down, you get all the sceptics shouting about how bad it is. The crypto market is all rush, all the time. This makes it bad as a currency market.
In general, I believe that a global decentralised currency is a good thing, but I suspect we may be a decade or more away from something truly usable.