Am I missing something? If you shoot 24fps for your video, I don't care the quality of the individual frame in terms of MP, RAW, etc. it's still a 1/24 second shutter speed (or slightly faster -- but if it's too fast, then the video will look terrible). What if you want 1/1000 to freeze action?
I suppose in the Jetsons-type future, we'll have all-in one cameras that do 8,000 fps, then post-produce quickly, algorithmically combining frames into an effective shutter speeds (i.e. combing 1,000 frames to simulate a 1/8 second shot) and adding/subtracting to simulate exposure for either video or photos (just push a button!). But that's some ways off.
But on a more personal level, I don't like processing video. The effort involved. combing through 24, 40 or 60 fps to find that "best" frame? I get tired combing through 300 shots from a days shooting. That would be covered in 20 seconds if you were shooting 30fps!
Also, as I think it was Nic or Luke who said -- video is a different medium. Forces you to watch the editors vision. Still open to interpretation, but photography can be even more personal to the viewer, and as the viewer, you decide how long/short of a time you spend looking at the image, or what part of the image.