The main advantage is cost. There are two main types of imaging sensors currently used, CMOS and CCD. CMOS has historically been used in digital cameras (because of the higher quality images it can capture, the lower cost, and the fact that digital cameras only have to capture a single moment).
CCDs on the other hand have been historically used in video cameras, with one CCD per color (3CCD) to increase the quality. They have been significantly more expensive and generally capable of lower resolutions, but had the advantage of capturing the entire frame at the same time.
Since CMOS sensors scan line by line rather than capturing a fixed image at a time, they exhibit an artifact known as a rolling shutter. This appears as a distortion when the camera is moving (particularly panning) due to the change of orientation mid-frame. Previously, the sample rates for CMOS sensors were too slow to allow their use for video, but as the technology has improved, it is now possible to sample quickly enough that, while still present, rolling shutter is not nearly the problem it was even a few years ago.
This has allowed for CMOS sensors to begin being used in professional level video, bringing with them the low cost, high resolution and high quality that had previously not been possible. The high end stuff still uses CCDs because it completely avoids the rolling shutter issue and an expensive enough 3CCD setup is going to still look better than the cheaper CMOS, but the cost savings now makes up for the rolling shutter issues.
The cost difference can be significant, with a price gap of double to triple in some cases for similar image quality for a static shot.