shifted keys are useful for admin purposes. for instance, being able to bring up the mame config menu (tab key) is very usefull for tweaking various settings....however having a dedicated button on your panel to do so is just asking for trouble. but if you have a shifted key setup as TAB, then you can still easily get to it by holding down your designated shift key and pressing the associated button. this keeps all of the admin type functions at your fingertips so you don't need to use a keyboard, but makes it so you don't need a dedicated button, and also helps keep people from messing up your config