The problem with shooters

The one main problem with shooters or fps or third person shooters is simply they dont have rpg elements in the game. By rpg elements I mean that there is not customizable guns or armour or even skills in shooters these days. I wonder why every awsome shooter like halo 3, cod 4, and gears of war dont they have RPG elements in them. Why cant I have my own weapons and armour. I do know that cod 4 has add this but it feels only half way there like why can't I change my armour or appearance. Why can't I change they way my character moves or how fast he/she moves. Sure gow, cod 4, and halo are great games but why can't they be even better with the rpg element in it, wouldn't you like to have you own armour and weapons in gears of war. Im not saying that shooters are bad but i am saying that they can be even better With a simple feature.