It's useful to black box some of the things when you are first learning. The specifics of serving a request are probably not the first thing you want to teach,

It's useful to black box some of the things when you are first learning. The specifics of serving a request are probably not the first thing you want to teach, especially when it requires some notional understanding of threading/blocking which Apache can take care of automatically. Also mod_rewrite and .htaccess provide powerful methods of adjusting behaviour of routing and the like.