Solidly knowing what the feedback means. Takes a lot out of the learning curve. For me teaching my boys, its easier to be able to say be in 2nd or 3rd gear, then saying when it feels right, shift to whatever's next, because they don't know what gear it's in. I ride with them and use my Cardo com to communicate.
It's no different than saying you don't need a speedo. Just feel the wind resistance and engine to know your speed. That's true and fairly easy if you've been riding for a while on the same bike and know from using a speedo what those sounds and wind feel like. The speedo helps you avoid a whole lot of speeding tickets, while you are "learning".