Snipers, or anything with long ranged scopes would completely ruin the game. It will turn exactly into DayZ, in which you'll get sniped by someone no matter where you are. It would just increase senseless killing.
As for the attachments... like J!NX said, this isn't Call of Duty. Weapons in this game are supposed to be post-apocalyptic, pretty much handmade. High grade military upgrades and attachments completely ruin the setting and gameplay. The military weapons in this game might not even be in the final version.
I for one if I had sniper rifles know that I would abuse the living shit out of them
now just imagine me with the mindset of trolling the shit out of people.