So far we know that the Structured Data was implemented to make the job of Google Bots easier since it is impossible for them to read and understand the content of a website that is in Hypertext Markup Language (HTML) but Rich Cards were developed to make the Google Search Engine Result Pages (SERPs) look inviting for the visitors with less emphasis on the content and more highlights on the aspects of it for which they usually search for.
Data highlighter on the Webmaster Tools is an advanced tool that is designed to be convenient for Bots and helpful for the users at the same time.
According to Google itself, this tool is made to teach the search engine about the structured data that has been provided to it but in a neatly classified way that ensures that the important details are highlighted and featured on the Rich Snippets.
As a website owner, your job is to use Data Highlighter to tag the important points of your content and Google will do the rest of the job of presenting it in an attractive, enjoyable, and easily understandable way.
Remember the time you used to highlight the important points in your answer books in the exam so the teacher would notice the important data instead of getting bored of your really long answer? This tool is similar to that exam time trick of ours.
The only difference is that search engine is not as smart as we were led to believe and in comparison to basic human logic, it is too stupid to understand human-generated content if it is not spoon-fed to it.
Though it was developed to find a common ground for the benefit of users as well as the search engine, it requires a lot of hard work from the website owners rather than making the process easier for them.
The reason behind that is the not-so-advanced algorithm set for its’ functionality which loses the highlighted stored data whenever there is a change in the site coding. It is not made to keep the data restored in the storage while the website goes through new updates and that is what makes it unreliable for most circumstances.
The most ideal one would be if you use it only for displaying the extremely important data and eliminate the need to highlight a large chunk of your content.