Work is not always about content creation, some people work mostly by consuming content (reading websites, browsing photos, selecting movie clips, navigating PDFs, or something else) and iPad is great for consuming content.
Well I can use the exact same apps on the Mac to do all of those things, so there is functional parity. But you get the advantage of a more precise pointing device, keyboard, and an OS that lets me easily have multiple things open at once. Video is certainly better to watch on a Mac, since it's got the correctly shaped screen and doesn't fall over when you set it down.
