It is because the only see this as an investment object - if you do so it is maybe right that the bigger fools theory could fit. But what they fail to realize is that this is really a big technological experiment where no company is taking the lead. Buying crypto-currencies is buying technology shares. Risky... yes, of course, but also with a fair chance of earning by being part of a new thing.
An interesting thing I have noticed is that many people regard big companies and other powerful organizations as a safe-keeper of their lives. They feel secure when a logo and a money tank is guarding them. This makes it clear why they have a hard time grasping this anarco-democratic p2p technology.
I don't think we have seen crypto meet anything like its potential for real use. Most of the growth is driven through speculation for now. It's still new technology, so let's give it a chance. I think a lot of the people behind it want to change the world.
Funny detail: in development nations crypto startups are actively invested in by telcos [with startup funds]. Because the unbanked ones.
If telcos decide to invest you know stuff is real. Even more so in development nations where mobile payments/remittances still happens via SMS because for many the telco wallet is the only bank account they have.
Some nations don't have the same banking networks we do and there may be less trust in such corporations. Crypto seems a perfect fit for them