While you might believe that, the market disagrees with you.

That is not true. For example I hold bitcoin. But I also don't believe that bitcoin will replace the financial system or will serve any real purpose in the future. I am just speculating on its value.

People speculate on loads of assets which have no real life utility. For example, art or classic cars.

Just because you are speculating doesn't mean other who also hold it are speculating. Personally, I hold it because I don't want my dollars to get perpetually diluted because of endless money printing, stimulus, bailouts, etc.

Also, Bitcoin has value and if you wanted, you unlock it and spend your money without even selling your asset, there was a discussion the other day about defi, highly recommend checking out MakerDAO if you want to have a practical use for your Bitcoins.