Because fps have one shot weapons EVERYTIME. I cant even think of a good fps that have 0 ohk weapons. Ohk weapons makes the game faster, rewards individual gameplay and punishes poor positioning and decisions. You may not like one shot weapon gameplay. But trust me...primary only pvp is the worst thing that ever happened to destiny. Y1 was the shittiest pvp experience of all times. And even with the ttk changes of y2, teamshot would just be even worse. (Btw in other fps you get one shoted from insane ranges, and you also get killed by 3 or 5 bodyshots of a smg and novody complains because thats how a fps is, kill or get killed, and not "oh i took a few bullets, let me go back to cover so i dont get punished for going in a lost fight")