If it helps, replace “practical problem” with “a problem customers will pay you to solve.” ARPANET had that. Bitcoin, on the other, never had an original sale. It was mined as a curiosity and then jumped from narrative (“currency of the future!”) to narrative (“store of value!”) to narrative (“mostly goes up!”)
Nevertheless, the internet turned out to be transforming from its original purpose. We can sit here and argue about cyrptocurreny but the game is young and we wont know what it will turn into in 30 years. Just like the people in the 70 and 80s didn't know how transforming the internet would become for our society.
Sure. But it’s still a customer making a purchase. That purchase grounds the project in someone’s need. A need they’re willing to trade for. The “trades for” part is important, since it references the status quo.
Financial assets, particularly speculative assets, don’t solve a need. They promise to solve a future need. (Sometimes they don’t.) Part of the discipline of speculating investing is knowing when to pull the plug.