Why do gyms have huge glass windows?

As I walked along a sidewalk in downtown Chicago I looked up at a large blue office building across the street and noticed the gym on the second floor.  The gym has lined up their treadmills and other exercise equipment right along the large windows.

We have all seen enough gyms to realize that this decision to place exercise equipment along the floor-to-ceiling windows is a trend, but the question we are asking today is: why?

What are possible reasons why a gym would choose to line up their treadmills and exercise equipment in the store front, behind large windows?

Here are a couple of ideas I had, just to get us started:

  1. The gym wants all passersby to be aware that the gym is there.
  2. The athletes like to pretend they are window-models.
  3. The people working out like to imagine they are out running on the streets outside. (In the gym pictured above they can also easily imagine that they have the ability to run at twenty feet above the ground!)
  4. An attempt to balance out the fact that most of us tend to put our “best foot forward,” cleaning up and looking good, when we go out in public; gyms provide the opportunity to see “normal people” looking sweaty and exhausted.

What other reasons might gyms have for this design choice?