Just simple economics, no need to get very deep into this question.
USD (as an example, could be other currency) has no limit, nothing scarce, it has value because people believe in it, it has history and is issued by an entity that is loosing the trust once had.
In the other hand, any crypto currency is limited, it's scarce, it's been almost 10 years since the creation and you can trust the technology.
Why is this still not worth trillions ?
There are forced transactions on fiat currencies (like the USD) which artificially increase demand substantially. In the states, all taxes must be paid in the national currency. Which means that the default currency for a business to use is going to be the national currency. Personal taxes and property taxes need to be paid in the national currency. So unless you are a currency trader, the default is to just use the national currency. People that don't know shit about currencies will use the national currency.
There are no forced transactions in cryptocurrencies. They are an alternative to fiat, and are optional. So you need to go out of your way to get a hold of it and use it. It will take time for those advantages to become clear, and for the infrastructure to be such that it is the currency of choice. If I have Bitcoin in Canada, where I live, I can't go into a store and buy anything. It's almost useless locally, unless you interact with another Bitcoin fan. The products and services that I need are sold in fiat, so that's what I need to use. Once Bitcoin adoption proliferates, then we can actually use it in day to day activities, and the demand will raise the price vs. fiat.