Your points are true, but at the same time wide IS practical in many ways--for more than just movies:
* Room for a document window plus palettes to the side. (And, I recommend, your Dock on the left.)
* Room for a work area on the right and a source list on the left (like iTunes, iPhoto, Finder, Mail, bookmark managers, etc.)
* You can (and always will) scroll docs vertically anyway--so at least make the width as wide as possible so you can view your file nice and big and sharp without any horizontal scrolling.
* First-person games are great in widescreen.
* Column view in Finder is the most useful view, I find--and great with extra width.
* Your menu bar has room for more goodies on the right.
* Even my 15.2" PowerBook screen CAN fit 2 documents side-by-side, and I often do. Not as nicely as a 17" or 30"
* Timeline-style editing is now common for consumers: there's iMovie, GarageBand, Final Cut Express, Logic Express, and many 3rd-party apps. And of course many more for pros, including 3D animation programs. So horizontal document scrolling/editing is very important these days, not just vertical word processing and web browsing.