In Learning and User Performance with Markup Menus from Kurtenbach and Buxton (1994), the document shows (https://www.youtube.com/watch?v=dtH9GdFSQaw) that the markup menus are: more efficient than the linear menu. And for me, they look just as intuitive.
What are the reasons why they have not been adopted by the industry? if not for the general public, I think the more powerful users enjoy increased efficiency.
Article Summary: https://people.eecs.berkeley.edu/~fox/summaries/ui/marking_menus.html