You do not know what exactly you do not know: one can't come up with 'OH what are the use cases for zk/crypto/whatever' unless they are looking for these use cases in a dedicated manner. Use cases do not grow on the trees (unless it is AgroTech) and do not fall from the sky (unless it is SpaceTech). If it was obvious what is the 100% use case it would be already built; and if it not obvious it means one had to connect some points to find the use case. But they do not know which points should be connected and even how many points should be connected. For some use cases, maybe two points are lacked, for some use cases maybe twenty points are lacked. It's a very hard job to look for use cases. It takes a lot of time, luck, and consistency. Because one does not know what exactly they are looking for and where to look for it. Yes, sometimes use cases are revealed by accident. But this is a unique edge cases. Way more often use cases are found because someone spent a good chunk of time looking for them.