Steven is only on set for maximum 3 hours a day. That's in his contract. So the shooting of the movie is only 3 weeks. Sometimes the director needs to move on quickly and can't wait before Steven has arrived back on set. That's when they use the double. And yes, also for just walking....It sounds logical. It's just Steven's fault. He has to put more effort in the moviemaking.
By the way, Steve Austin wrapped today!
Another thing. It bothers me that everyone of the cast and crew are so enthousiastic and Steven is not. They tweet everyday and are posting some pictures online. But you never hear something from Steven. Come on Steven, this is your movie!! Like he said in Born To Raise Hell: If you wanna be a police officer (in this case an actor) you gotta be on the ball!!!!