Stage crew are as vital to the performance as the actors onstage; I know this for a fact.
For this past spring’s musical production Jukebox Diner, I was the only stage crew.
For that, I had to check props, set the stage, and have the food cart prepared. I followed the script in case cues were needed. Between scenes and acts I reset the stage, cleaned, and had the correct props placed. After curtain call I prepped the stage for the following night, did dishes, and swept.
Besides all that are rehearsals, set building, painting, and practices. Crew members must be patient, have a flexible schedule, think fast with solutions for problems that arise, and be able to be part of a team.
While it’s demanding, it’s worth it. Personally I do stage crew because I like to help entertain people. Stage crew and drama in general help people get out of their comfort zone. I can watch and hear others act. Those elements get lost when on stage acting.