It's as accurately representing the actual game state as much as possible. Thus why things such as MAMEHooker are supported, such as they are, by the MAME devs.
Some games actually REQUIRE the artwork to be functional, as well-- Spy Hunter has five separate lit pieces of artwork detailing car status, for instance.
Ok, when you say "game state" you mean whole cabinet, I mean just PCB. It's because I wanna play it in a cabinet and you wanna play it on a PC.
You make a good point and yes it's nice to have it all done "digitally", it's just that I believe you should preserve "wood" by restoring wood, and restore PCB by replacing it with PC, so that PC needs to do only what original PCB did.
In any case I am not suggesting to remove these features, just separate their source code from the main core build, make it more like some "plug-in", move it from run-time to be compile-time only options in order to make it easier for the development and is overall better design for such huge & public project, I believe.