I understand. If it's mandatory informational or community volunteering, there's not much drive to invest heavily in a particular skill like make speaking production value into quality infotainment.
When it's a skill interesting or essential enough to improve it might be worth for speakers to move around trying different support organizations to get new perspectives, and different techniques and feedback.
I’m not consistent, so I’m not on anyone’s shortlist for keynote speaker, which is fine by me.
For classes, though, I practice for hours. It seems to satisfy people.