Little to no learning curve, instant communication. A sharpie is still my go to tool for wire framing and storyboarding.

Many designers know: the best design tool is a marker. Not Figma, not Sketch and no, not a pencil. With markers you draw something once and it’s done. No erasing, no fiddling around, no details. You get your big idea on paper in a few seconds. If it’s not good enough, you try again.
Bringing markers back to UI design