I am convinced (because this is how I personally feel) that it is because it leads to less psychological stress. Choice is a very hard thing to handle I think for humans and often leads to stressing out over the choice itself rather than the outcome of the choice.
There is a reason people pack their bag full of gear before they head out, just to end up using a single body and lens combination, it has happened to me several times at least. It's simply because I cannot handle having to make a decision upfront, because I don't know what to expect when I get out there.
I also think it's nice because in many cases you only need one lens and one body - but I believe that because I think most of us tend to shoot similar shots all the time. And I don't mean that in the sense that we always shoot flowers for example, but rather that we tend to take the same view point and perspective when framing because it just comes natural.
It can be argued that you need some lenses for certain things, which I guess is a "fact". But in those cases, there is no stress in making the choice, because it is no choice, you "cannot" photograph something really really far away with a 28mm lens.
Anyway, on a personal level, I constantly strive for as little gear as possible, because I can't handle choices. 🙂 It's the same thing with everything, I hate having two computers, I hate having remote controls with loads of buttons, I don't like products with many ways of doing the same thing etc.
But in the end, I think it only works if you are somewhat uniform in what you shoot. When I had my DSLR, I only had two lenses, one 50mm and one macro lens, because back then that is what I needed to have to shoot the stuff I enjoyed.
Then I grew tired of macro, so I sold the DSLR, got an M9 and now I have a 50mm and a 35mm, but I am thinking of selling the 35mm because it only stresses me out, and in most cases I have no actual use for it..
