Semantic enrichment of scientific literature seems promising as a way of unlocking the huge amount of knowledge in published documents (e.g., articles, textbooks). However, getting the enrichment process right takes a lot of effort and the enriched data doesn't provide sufficient value differentiation to 1) be worth the investment and 2) be commercially viable.

This author focuses bio-sciences; I've been collecting a list of similar efforts in Physics [0]. Those who can't do teach, and those who can't teach decorate data with semantic features.

[0] https://derivationmap.net/other_projects