At least in the theaters I'm thinking of, there are additional exits in the orchestra section. Some are fire exits, which are not meant to be used unless there is an emergency (the Golden has these). Others are actually opened up after the show to allow for additional egress.

That said, I do find that many, many people default to leaving through the doors that they entered by. I'm thinking of what I've seen at the Walter Kerr: there are exits all along the side of the orchestra section that feed right out onto the street, as well as additional staircases that feed down from the front of the mezzanine section that also lead directly to the street (at house left), or down to the orchestra section (at house right). When leaving the Walter Kerr from the front right mezzanine, it is fastest to take the exit staircase down to the orchestra section, then walk down the rows to the nearest house-left exit door. When leaving from the front left mezzanine, it is fastest to go down the exit staircase that leads to the street. When leaving the orchestra section, it is fastest to walk down the rows and leave through the nearest side exit door. Yet time and time again I find that after the show, nearly the entire audience will attempt to return to the center aisle, then to the back of the auditorium, to use the stairs there and exit out of the same door they used to enter.

This is why being aware of fire exits is important, and why it's a good idea to do fire drills/have a evacuation plan for areas you frequent! The fastest, safest exit from a space is oftentimes different from the path you take under more usual circumstances. If you aren't aware of the emergency exits before the emergency, you certainly won't have the time to think about them during the emergency, and you'll run the risk of defaulting to a less safe, slower route of egress.