Today the OS has to support way, way more different hardware than BeOS and Symbolics ever had to. BeOS made their own boxes right? Symbolics certainly did and I doubt they had a TCP/IP stack build in....
Be did initially make BeBoxes, but BeOS later ran on off-the-shelf x86 hardware (provided it had drivers, of course, but basic graphics worked on pretty much anything of the era). BeOS R5 at least also had a TCP/IP stack, and while it wasn't highly regarded (Be was rewriting it when it went under) it more or less worked.
By this argument, OS X should be a lot lighter than Windows, which it isn't.
