Many of the mirrow shots were developed to give new angles to the cramped conditions of the cameramen. The cameras they used were HUGE compared to today's video cams; the zoom lense assembly weighed about 60 pounds by itself. The Norelco Cams that they used after color came in on the show were the new industry standard, but they were cumbersome. They used wheeled camera bases with hydraulic lifts to help smooth their movement, and these took up a great deal of space as well. Stuart Goodman, who worked on DS recalled that the zoom took some getting used to, but was ultimately smoother once you got used to them. I think some of the lingering shots were to buy time for the next camera set-up, and many of them were, indeed, artsy shots to add interest to the show or mood of the show.
Petofi