If they are 'infected' and not zombies, then why do the devs call them zombies in the patch notes? Pretty sure they are zombies... Also the 'Z' in dayz is a rather obvious hint don't you think?
I'm pretty sure it's the M68 that can have a battery attached to it. I think later on you may require a battery for the red dot to work. If you right click the scop it allows you to turn it on and off.
I think It's because in RL, when do (most) people ever get the chance to shoot somebody? Never. Same with racing games/sports games etc. Most people can't do it in RL, so we play a game for the experience. Simple.