Have you ever used a 30" display? Maximizing windows does not make a whole lot of sense there, especially considering the difference in window contents on Windows vs Mac (ie. self-contained menubar, etc).
Hell, what proportion of them use desktop-variety computers?
I maintain that people think of multi-windowed UI in terms of windows first. Resizing a window to fit the content makes less sense than resizing the content to fit the window. People also seem to get really upset when UI interaction isn't consistent, and the Mac approach means that it varies wildly between apps.