what are these reasons and can you elaborate more about the 'system of logic'? and wouldn't it be inaccurate to say 'in Windows' as it contradicts your first sentence mentioning that this 'system of logic' only applies to Safari and iTunes even in Macs?
Sorry, in regards to Safari and iTunes I was referring to the Mac. Yes, Apple's Mac OS system is based off a system of logic. The Mac OS is document based and Windows is application based. In Mac OS, using Safari, if the content on the web page fills up the entire screen real estate, Safari will maximize to full screen to cover as much content as possible without producing the horizontal scroll bar.
If the content on the web is minimal say like in Yahoo.com which never takes advantage of the entire screen real estate then Safari will maximize only enough to cover what's on the screen. It makes no sense to fully maximize the screen if the content leaves wasted space on the left and right sides of the page. Some web pages just show the content on the left side, leaving the right side with wasted space. That's why Apple builds Safari that that way.
In Windows, everything maximizes when pressing the expand button even if the content won't fill up the screen. It's not logical that way, but because it's application based the Windows OS is designed to truly run one application at a time which is why everything will maximize to cover the whole desktop.
Personally I don't maximize my web browsing to full screen, even when I'm using Windows. I feel claustrophobic when I have no access to the desktop.
iCal, iMovie, Garageband and everything else that comes on a Mac will maximize because the content involved will will up the screen.