Facebook [... was] updated on day one.
To be fair, the Facebook app is just one big scrollview/webview. The scrollview/webview just needed to be scaled to the new screensize and boom, it's done. Heck, they probably just resized the parent view and had IB auto-adjust all their sub-views in about 2 seconds.
At most, they had to redo the blue splash screen. Probably took them less time than it took me to redo my custom self-made wallpaper, which was about 10 minutes using my old .psd file.
Finally, their app being just a big "browser", it can easily be test with just the simulator. No snazzy multi-touch gestures there, no custom input code, no sensor usage (the scenarios are limited with the simulator, really need device testing for those).
Some apps are much more complicated, have much more custom art to redo, not to mention UI layouts that can't just be scaled, use the phone sensors to their fullest, and have some fairly complex gesture support. Those are going to take more work and as was said, we got the iPhone 5 enabled Xcode pretty late, not to mention the phone was announced on the 12th and even iPod Touch devices were not available quickly for testing.
You really have to have done some iOS work to understand how this can be a 5 minute fix, like it can be a couple of months of work, if it's even worth bothering to do in the first place (I can bet you a lot of older apps just won't update at all, works perfectly letterboxed).
I completely agree with you that storing and managing a disc library is something that I'm happy to do without.
I'm the opposite really. I really like managing and manipulating the physical discs. All the boxes sitting neatly organized on the shelf bring color and contrast to the decor, opening the movie, looking at the disc before inserting it, it's all a nice experience to me somehow. Just streaming crap from my NAS isn't the same, it's like a cheap thrill, it's not "sitting down to watch something", not even close.
Not to mention Netflix's canadian selection sucks.