[Question] Why cant classes acces objects on stage?


Im trying to get used to packages and classes in AS3. Im used to put all code on the first frame of the timeline, but now i have 442 lines of code on the first frame. Yeah 442. And this is for a game engine so i thought i should put it inside some classes to make it easier to read an reusable. But i have noticed that if i create a class called Code and make a instance of that class like this:
[AS]var codeObject:Code = new Code();[/AS]
i get a bunch of errors because the class cant Acess the stage and the display list. Why??
i found a workaround by linking the class to a movieClip and and do this:
But im just wondering why classes cant acess the stage:h: Anybody knows why??