Why do cartoons and other American shows never change openings?

[Kasz216]

Soriku said:

RolStoppable said:

What does qualify for changing the opening in your opinion? Does it have to be more than a longer or slightly altered version?

EDIT: Oh, you are talking about songs here.

Not just the song...scenes too.

They change the scenes... where applicable.  If a character dies, stuff like that.   Otherwise... why bother?