I hear this all the time when I teach poker: "Alex, why are you showing me all of these percentages? I play live poker all the time. I won't have a HUD there. How will I be able to use these?"
"Oh, that is where you're wrong my friend!" I tell them.
In reality, I use percentages as a form of shorthand. It would take me a long time to say, "All pairs, suited connectors, suited-gappers from -suited and up, Broadways down to but not ..." and so on. Instead, I give rough percentages in my lessons.