Because it is the most well-liked, and because marked contented will probably be verificable/auditable concurrently by humans and machines. You'll want to observe the general structured information guidelines, as well as any guidelines particular to your structured facts kind; if not your structured data may very well be ineligible for https://rafaeluejpt.blogoscience.com/38064008/the-5-second-trick-for-product-schema-example