Many of the commenters here have pointed out that the semantic web did not become popular because the incentives are not supportive of the investment. I agree,

Many of the commenters here have pointed out that the semantic web did not become popular because the incentives are not supportive of the investment. I agree, and this leads me to wonder if there are domains in which the cost of investing in semantic markup are relevant. I see scientific publishing as a venue that could clearly benefit from application of a semantic web-like domain-specific approach. There are a variety of possibilities [0], [1], but again many are implemented behind proprietary paywalls. There's value in search and knowledge representation, but the prohibitive cost of implementation is challenging. [0] https://en.wikipedia.org/wiki/Semantic_Scholar https://en.wikipedia.org/wiki/Semantic_Scholar [1] https://en.wikipedia.org/wiki/Web_of_Science https://en.wikipedia.org/wiki/Web_of_Science