Flags are ingrained into our community. You are obviously going to get fucked, therefor you flag to the person most likely to sodomize you. Success! You are alive and well. Then, a challenger appears! Cripples the color you flag to, thus you are fucked once more. And to preserve your precious points on your 100 point table, you flag switch. As in flag to a different opponent after flagging to another. Not the double flag, that's entirely different. What say you, Batman?

TL;DR: Flag switching is the new early flag.