People who don't have social/public speaking anxiety do not understand how truly bad it can be. Of course no one likes giving presentations, but some people just get a few jitters and are able to easily brush it off. For them, practice makes perfect. For others, standing in front of a group of people can create a serious fight-or-flight response that can be crippling. For many people, including myself, this feeling never dissipates, even slightly, no matter how many presentations you have completed.
I'm ashamed of it, but this fear has caused me to purposely avoid tons of great jobs that I know I would love.