Mainly because it breaks the photographer’s back.
Here is part of what I am bringing to a multiple corporate headshots session tomorrow:
This kit consists of:
- One backdrop
- Two rolls of backdrop paper, grey and white
- One two-monolight set with three stands and two umbrellas
- Two more monolights
- Four lightstands with umbrellas for speedlites
- Camera kit (lenses, a Canon 1Ds MkIII, etc)
- Lighting kit with four speedlites, five Pocketwizards, modifiers, and much more.
- a 60×80 softbox
- a Canon 7D camera
- a muslin backdrop
- a stool for the subject to sit on.
I am now going to bed early, so that I can build strength!
The serious point, of course, is that when a photographer visits with a portable setup, he really carries with him a full studio and everything that includes.