Grumpy Scot

Question: There is a scene in the movie in which Arnie disguises as a woman to pass the entrance control in Mars. Moments later, the mask he's using starts to malfunction and he has to take it off. When he's doing that, we can see that the man who's playing Quaid is not Arnie but a stunt double. Why did the director choose a stunt double to replace Arnie in a scene that's not risky at all?