Some people do, but camouflage clothing is less important at 'invisibliity'.
There are some who wear ghillies on the scenario or walkon scenes, but they can be doing so for a couple of reasons - there is a psychological element to wearing a ghillie suit - the opposition may think that you have a 'sniper' hidden somewhere or a sneaky type coming around the back if your home base, at our Falklands game there was a guy in a Jack Pyke light 3d leaf ghillie - he was running up front with the majority, but when he dropped into the edge of a bush on a path etc he vanished, not only did he have the ability to stay still and wait but he had the precise colour mix for the venue & time of year.
People are less likely to wear a complete set of camouflage as the 'right' uniform, thats more of an airsoft or milsim thing, you can hide just as well dressed as a power ranger if you pick the right spot and act correctly, or be highly visible in camouflage if you stand in the wrong place or dart around.
However camouflage does have its uses. People have criticised MTP / multicam as too bright and not designed for European woodland as DPM was, but we have (sort of) prooved MTPs effectiveness when we filmed 'How to surviive a disaster movie' with our sentry gun. The software uses artificial intelligence to identify valid targets and to select where to aim, sometimes going for the best chance of a hit with shooting at the torso. We don't just have the results of a hit or miss to see how effective it is, but it also takes hi-res photos showing target selection and tracking. In lining up the shots and testing out scenes I was the stuntman dressed in MTP/multicam/DyeCam and with blue digicam goggles. So it was not much surprise that I was regularly shot in the goggles. The presenter also wore MTP/multicam/DyeCam but camouflaged goggles - he was also taking shots towards his head, (and a nice triple neck rub).
He was doing all the tricks to try and distract the tracking & target recognition - but it would always track back to his head - our looking back at the targeting photos gave the impression that the pattern would disrupt recognition of a figure and render the head the easiest thing to track and select.
http://www.channel5.com/shows/how-to-survive-a-disaster-movie/episodes/man-and-machine