Photos have simply become a by-product of the video stock footage production. When one films or shoots a time lapse sequence, it usually yields at least 300 or more fantastic photographs as these then become such a sequence. What better opportunity than to extract the best of the best of such a sequence and offer them up as fine art or commercial photos. Of course as the equipment has become more powerful over the years, the opportunity exists to quickly switch between shooting video and photo. This again yields in many by-products of both. The upside is that one can literally play both roles of photographer and videographer simultaneously. It's all in how one "frames" it, I suppose.
A Sampling of the Variety of Imagery