I would add that something as complex as a web browser would be impossible on the Mac App Store anyway -- a sandboxed browser wouldn't even be able to open file:// URLs.
Berners-Lee's original web browser was developed on the NeXT (direct ancestor of OS X)... But if he wanted to take that 1991 browser and distribute it on the Mac App Store today, he would have to remove important functionality.
Impossible on the Mac App Store, but perfectly possible on the Mac. Which is the appropriate comparison. Tim's web browser wasn't released on the NeXT App Store, after all.
Well, yes, web browsers are possible on the Mac. They are probably the most commonly downloaded type of Mac app.
Which begs my original question: what good is a "Mac app store" that can't accommodate Mac apps?
Apple isn't alone in this, of course. The Windows 8 app store (Marketplace, or whatever it's called these days) is just as limited... But really, if the most apt comparison for the MAS is the Windows 8 store, that further illustrates just how badly Apple has blown it.
Berners-Lee's original web browser was developed on the NeXT (direct ancestor of OS X)... But if he wanted to take that 1991 browser and distribute it on the Mac App Store today, he would have to remove important functionality.