I think it might be the proverbial fast boat in a narrow stream, the narrow stream being ruby the language. It's not a mainstream one, and frankly the main rea

I think it might be the proverbial fast boat in a narrow stream, the narrow stream being ruby the language. It's not a mainstream one, and frankly the main reason to learn it in practice is rails. There's a big cold start problem there. You have to convince people to like both the language and the framework at the same moment of decision, in addition to committing to learning both at once. That's just always going to be more difficult than selling only a framework to people who either already know, or see more value in learning, a more mainstream language like JS, Python or Java. I think this is the biggest reason it's remained niche.