Even those who volunteered and got turned down for active military service (Ronald Reagan) found a way to help.
I'm not sure of the terminology, but I don't think it's accurate to say Reagan wasn't in active military service.
Due to his eyesight, which was truly awful, he wasn't eigible for combat duty, but he actively served in the Army Air Corps for several years making training films and performing other services, which were presumably helpful to the war effort. I think that qualifies as "active service," or at least as active as any other serviceman not in a combat outfit. (Which not everybody can be.)
I had the honor of meeting Jimmy Stewart and talking with him for nearly 20 minutes. He was truly a gracious gentleman and gladly recounted some of the hollywood stories that he must have told many, many times before.