cost.

If by HDD, you mean hard disk drive, the DV cameras rarely use them because there is too much data coming too fast from an HD camera. The cameras have to compress the video to fit it on a tape.

The Canon HD camera can output to hard disk, but I've been told you need a fast processor and a disk array to keep up with the data coming from the camera.

You don't buy cameras for 'years to come' anymore. Three to five years is about the expected life.