Well, I just delivered a full day Child Safe Environment (formerly Mandatory Notification) training to five co-workers and I think I did a pretty reasonable job of it. I remembered the main information and I felt pretty confident as I went over all of the details and took the interruptions and problems rather in my stride as I did so.
I think I have two things to thank for that sort of confidence and easy-going public speaking attitude. One is my experience in a Youth Theatre. If you can take pride in looking like a nonce then you can deal with teaching people to a powerpoint slide. The other includes my years of experience as an ST / DM / Keeper, particularly in LARPs.
I mean, think about it. You get used to dealing with several genereally rowdy, recalcitrant players who can all think of something better to do than your particular game plan and like to drag the game off-topic. You're used to standing up, keeping their attention, and trying to keep them focused. You're also used to everything not going to plan and having to either come up with something on the fly or graciously explain why you don't know the answer to that.
So yeah, the next time someone wonders what you could possibly get from STing / DMing, you now have a response.
Public Speaking and Trainer skills!