The whole point of an economy is that something has value if it's valuable to someone, not just the person who's holding it.
I'm not going to use a chunk of gold for anything, but it has intrinsic uses that aren't tied to being an exchange of value. It can be used to make jewelry, electronics, food, and medical devices. In some of those applications, there is no substitute for gold.
Contrast that with Bitcoin, whose only value is speculative (whether people think it will increase in price). It has literally no other use or value. If the internet crashed, you couldn't sell your Bitcoin to someone to make jewelry out of it.
I see crypto as a "digital asset". It's something you store funds in to hedge markets or get around transactional issues (either because you're doing something potentially illegal by some entities definition or because your currency is shot to shit), which basically makes it like golds or precious gems.
I'm not totally sold it'll last long term, but I don't see the comparison as a huge logic leap.