Cameraman-interviewers don't use AF NOW because there isn't a good system available. Canon's DPAF can change that, and many one man bands are already touting the 70D, and C100, for this very reason. So, what was true yesterday, won't be true tomorrow, and some of it isn't even true today.
Careful now...it sounds like you're dangerously close to suggesting there's something innovative about Canon's newest CMOS sensors. You might get some flak for that wild idea...
LOL .... lots of flak ... manual focus is like the 11th commandment to video people. The DPAF technology is brilliant, and possibly revolutionary to video as they perfect it, and I am looking forward to seeing it full-sensor on upcoming Cx00 cameras.
I think the day when automatic AF systems can be programmed ahead of time to focus either on certain subjects at certain times, or to certain points within the depth of field at certain times (or maybe just at the push of a button), then the 11th commandment will happily be broken by a lot of video people. I think the main reason why manual still reigns supreme is that for many use cases, you pre-determine where your going to be focusing during a shoot, and pull focus from point a to point b to point c smoothly and at the right times and right rate during a clip.
I think the big deal with DPAF is you could track focus in a subject moving front to back in the depth of field, which from what I've seen, is probably the more difficult job for a focus puller (or the camera operator, if they are pulling their own focus). I think if QPAF comes along at some point, that will be when the accuracy and consistency of such focus improves to the point where it could really be relied upon for critical video work.
Reviewers claim that the DPAF in the 70D doesn't hunt at all, and tracks fairly well. Combine that with touch screen to spot focus and it is extremely powerful, eliminating the human error. They need to provide really smooth pull, and variable focus speeds from slow to near-instant. Programmable timing isn't necessary because the camera operator can trigger that for planned shoots anyway. I think this is all coming sooner than later. Even magic lantern has programmable focus pull points, albeit a bit kludgey.
Tracking is another good use of the DPAF, but for me the biggest is just the fact that I can focus my attention on interviewing while the camera compensates for the subjects movements. I could even get three camera angles in focus while interviewing as a one-man-band, or a single cameraman can setup and monitor two cameras, especially with wifi control (sit at one camera, and operate the second remotely, including focus).
The more power, the better.