pretty much this. It seems both are becoming important, so cataloging them together does make sense. I actually don't mind it if it is not at the expense of performance and bloat.I can think of two reasons. First, just to catalog and preview it (if they can get it to work right). Second, because Aperture can.
What you can do (in LR 5 at least)- and this can be quite useful especially for underwater video - is toI believe you can trim the ends, and capture a frame into a jpg.