Probabley why HiTech hasn't implimented rear view mirrors yet - why double the number of sun complaints?
I'm lazy so I'm not looking for the post. HiTech said one of the reasons for no rear view is the need to 'duplicate' the world. In other words, the world you see with out a mirror is one and the one in the mirror is two. He described a large headache in trying to accomplish it and making it smooth for players at the same time.
Imagine those poor SoB's who get a low frame rate with all graphics toned down with a single world emulated, trying to suddenly run two worlds.