On paper you have a very good point. However, TV cameras tend to be positioned in different locations than a stills camera. Their shutter angles are also not usually optimised for stills extraction (as far as fast moving objects go). They usually shoot wider than the photographers do. They also tend to not move around a lot. Having said that, just as DSLMs replaced DSLRs, so too will constant recording replace single frames for acquisition. So you'll have photographers but they won't necessarily be taking single frames. Already you have Olympus and Panasonic cameras with pro capture modes, which have something like a one second buffer. So it's part way between photo and video.