Guests?

Why doesn't most, if not, every game that features online multiplayer have guests? I mean, come on, think about it, if Call of Duty 4 had guests it would've been improved by about 20% in my opinion. That's the only gamer i can think of, but i'm almost certain there's more. Discuss.Guests?
I know that's an issue for me with COD4 although it's a minor one. I wonder if it's a framerate issue. Having 4 screens going instead of 1.Guests?
The reason you can't play ranked with guests is you could cheat e.g just kill the geust over and over to gain exp. if the guest is on the other team that is
[QUOTE=''TehAssassin8'']The reason you can't play ranked with guests is you could cheat e.g just kill the geust over and over to gain exp. if the guest is on the other team that is[/QUOTE]And this has to do with....? I'm pretty sure most games with guests (Halo 3) Only allow the guest on your team, and even then, you're only allowed to play socail with guests in Halo, which is fine by me, especially considering social games have a far more relaxed pace and feel to them.
[QUOTE=''TehAssassin8'']The reason you can't play ranked with guests is you could cheat e.g just kill the geust over and over to gain exp. if the guest is on the other team that is[/QUOTE] this is not valid he never said ranked

jane iredale