I was fortunate to have met David Prowse and get his autograph while volunteering at Dragon Con. A really cool guy. There were rumors circulating among the staff that he and other actors/actresses were attending sci-fi/fantasy/gaming conventions even when they weren't paid to appear as guests. Why? Because that is how much fun those events were! Meeting the fans, attending their room parties, their dances, and well just being fans themselves. Below is a link to Dragon Con's experiences with this fine person.
https://www.dragoncon.org/dailydragon/dc1999/the-history-of-david-prowse/