Using structured data on your site is a brilliant way of making it easy for search engines to find you. What is structured data? This is just a clever way of putting tags around content such as text to help machines better understand what the content is all about and how it relates to other content on the web. You have loads more content you can tag too, videos, events, products e.t.c
If it all seems too much to understand you should not worry, https://schema.org has large amounts of resources that can help understand structured data better. You can also find examples on how to use structured data on there too. Now that we have shed some light on structured data, lets look at why every site should have it. If for any reason, then for the fact that structured data aids Google to find you. This gives you an edge over others who may not be using it. SERPs now publish rich snippets so as a way of getting better rankings structured data would be a safe bet.