There are several reasons why people are constantly asking for structured content or content structures in the TYPO3 core for a long time.
Sometimes a flexible use of multiple columns or maybe even more complex layouts to structure content is required. Some use cases developers/ integrators are often struggling with are flexible accordions, content containers as content elements, restrictions on content element placement and drag & drop. Unfortunately some of the current solutions have often led to problems with upgrade or migration.
On top, TYPO3 should provide a semantically correct way for defining custom content types.
This initiative was inspired by forge epic and blueprint, but will provide its own concepts for the goals.