The main arguments studio photographers make against outdoor photography is either 1) the background will be distracting, or 2) with uncertain weather, the light is unflattering. Since I shoot in my studio as well, I’m not purely an outdoor photographer, but for argument's sake, I will address these concerns as a representative for all outdoor photographers.
I’ll speak directly to the studio photographers (but you’re free to listen in)-
1) Distracting Backgrounds
Your argument about distracting backgrounds is legitimate if the photographer has no idea what he’s doing. If I pick up a point and shoot camera set on automatic, the shots won’t look so great. But I don’t use a point and shoot, so it’s not a problem. A great background is flattering without drawing attention to itself, and that can be achieved inside or outside. The background colors should bring out the client’s eyes, hair color and skin tone and make the photograph more interesting as a composition. The variety of locations available outside makes this much easier to accomplish. As you know, agents' trashcans are overflowing with headshots that lack these qualities, and they’re usually studio photos.
Here are a few examples that show a variety of outdoor backgrounds-
2) The light and weather are uncertain
Photographers who find natural light to be unflattering or inconsistent just don't know how to use it, plain and simple. The best studio light aims to recreate natural light. Of course, natural light changes every minute, location photographers need to be comfortable with all conditions, and the weather changes constantly, especially on the east coast. Sometimes it's cold and sometimes it's hot. This just means I need to shoot quickly and take lots of breaks - it's an adventure, it's spontaneous, and it's unique to each person. I'll take this any day over a laborious studio process that consistently repeats itself.
Interior light-
Back light-
Direct light-
Overcast day-
Sunny day-
Rainy day-
Snowy day-
Postscript
On a personal note, I'd go crazy shooting with the same set-up, in the same room, every single day. I'm pretty certain that I'd get to the point where my fake backdrop would start talking to me, and I'd pull a Jack Nicholson in The Shining, completely flipping out and chasing a client through a giant hedge maze. Shooting outdoors looks less like this:
And more like this:
And in my book, the latter beats out the former any day.
