There are 2 types of pws, one that can speak more or less fluently when they're talking to themselves (or talking to their pet), and another who stutters regardless of the situation. For the former, their stutter is characterized more by social anxiety, and once you start speaking up more and more in front of others, in front of audience, etc. most of the stutter goes away over time. For the latter, they have much harder time speaking fluently regardless of how much exposure exercise they perform. I suspect most of the celebrities you hear about are of the former kind. So if you fall into that category, you can also start looking into excerise for social anxiety like CBT to increase your exposure to these stutter-inducing situations, and gradually improve your confidence, reduce fear, etc.