The idea is to have on all dialog windows the same shortcuts available. Also the wish is to have a documentation which shows all actions which are with shortcut available.
e.g. "Esc" for "Cancel" or "Enter" for "Ok".
At the moment in some dialog boxes "Enter" work for "OK" and in other dialog boxes it don't work.
The point is that in Windchill many windows open and so shortcuts can help you to push up you performance (some users like to work with shortcuts).