In a world without the concentration of development to venture capital-backed tech firms, semantic models of data create a web of rich APIs and data that are interlinked and that can grow and evolve.
You have schemas for representing people that you can download as contacts. Schemas for representing articles that can be linked to people. Schemas for comments and upvotes... Fully distributed Facebook / Reddit / Twitter that anyone could extend.
Venture-backed startups grew faster than the Semantic Web. That's the reason it didn't materialize.