It is possible to maximize a safari window.
If you want to do this make a bookmark with the following in the address section: javascript:self.moveTo(0,0);self.resizeTo(screen.availWidth,screen.availHeight)
This will cause the window to stretch as far as it can. I have it set on my bookmarks bar in Safari. Works great!
If you think about it, maximizing is a bit silly really. For the most part you end up with a load of dead space. As you will soon find out, mac users don't like wasting space 😉 😛