Because most people think that in order to solve the problem of a cryptocurrency, they have to also solve the problem of who gets money when you print it.
Far too many people conflate the need for electronic cash versus the need to improve upon how systems like the Federal Reserve and their International equivalents work.
Honestly, as a software engineer who understands some basic economics, I think cryptocurrency becomes far more interesting when it's not trying to solve the problem of who gets money when it's printed.
I also think that the Federal Reserve, and its international equivalents, work very well for me! I think that trying to come up with a currency that improves upon the Federal Reserve System, or equivalent, needs to be a separate technical problem than just trying to have an electronic form of cash.
In my opinion, most of the people who were excited about cryptocurrency were scam artists, the kind of people who just don't understand how money really works, or engineers who don't really understand scaling.