What are the benefits of using Microdata in HTML5 tags?

Adding microdata to Web pages helps search engines to better understand the pages' content, their topics, etc. The main purpose of microdata is Search Engine Optimization.

This information is not visible to humans: it is pure semantic information. Popular kinds of microdata are events, a person's profile, the description of an organization, the details of a recipe, a product description, a geographical location, etc.

Yes as explained by other experts it is helping Google Analytics for meta tags and serves the purpose of sitemap as Google Base in earlier days would help in search engine rankings

Using Microdata on your website helps search engine to show your specific website data on search results. This helps or guide user to click on your website, if he/she search for specific thing. This will lead to good CTR and less bounce rate.