I think you are the most detailed poster in this forum, am saying this base on every other post of yours I have come across.
That being said, you are absolutely right, why not invest that disposable income in something that will bring great value in years to come than spend it on things that will lose value the next day or so.
Despite having the ability to form our opinion as humans, we can also get ideas from others' opinions too.
Investment is all about being smart and setting some boundaries so you don't end up losing it all because of being overwhelmed. You have really made a valid point.
I am not entirely sure if "disposable" income is as disposable as you may think. In this day and age, we are living in a world where crypto is making things a bit more volatile than it has to be. Look at all the other things people can do with their money, and realize that it is not as great as you may imagine.
For example, if you bought 100 shirts and sold it on a concert, you would have made a lot more money right? Business is still the king, you are not going to start off with 100 bucks or 10k bucks whatever and become a billionaire via crypto, but business ideas makes that possible. Crypto is and will always be great for long term investment option, but the volatility makes it questionable.