[Skunkmeister]

To answer your question as to why we do it, its because the game by default has really dreadful looking markings, and since many squadrons that operated certain types are NOT represented in the game, its much easier to apply it directly to the aircraft and make it look as though it was part of it, rather that just slapped over top of it.

Many skinners often include blank versions of their skins, just so you can use the default in game crappy markings if you feel like it.