Let’s be honest here: if all you do is sit in your car listening to podcasts about the rules of hockey, don’t expect to be Sidney Crosby.
Public speaking is a physical activity – like hockey, football, or soccer. As a public speaker, you are a type of athlete because speaking involves physicality, muscle memory, and humanity. Your presentation needs to be in your body in the same way you have “Happy Birthday” in your head. Practice gets your ideas into your body, so that you can call them forth at will.