Buddy of mine says he uses them because he can't be assed to remember 10 years worth of content, 100+ trials/dungeons/raids etc, especially in EX and above. He knew the mechanics when they were relevant but has since moved on to current stuff.

The callouts are just a little verbal thing that helps his brain remember. And you know what? I can't fault him for that. This game has a massive backlog of content that you could be thrown into if you do the roulettes regularly.