A lot have happened to HTML since I started with web development in the 90's, but I'm still waiting for the semantic web to catch on ... One problem is the rule of least resistance, people will usually do as little markup as possible. Adding schema itemprop etc is a lot of work for very little gain. The only effect is that it's now easier for Google to scrape your web page to show the data in the search result, instead of sending the user to your site. You offer free lunch, and your biggest competitor takes it all, then sell it for profit. For this reason, sites like Facebook and Linkedin make a lot of effort to make it hard or impossible to scrape data. There are also a lot of other sites that keep hugging their data, walling it off from the rest of the word. This is why the sematic web have a very hard time, even though it's such an great idea.