Those kind of shooters do exist though, Arma being the prime example. Players often joke that it is a walking simulator despite being somewhat constrained in favor of a fun game over 100% realism. But you can easily spend 30 minutes hiking to the next objective just for a chance to take a shot at somebody or get shot in an ambush. It isn't conducive towards a quick 15 minute game, but it is very much a different style of game with people sneaking and hiding and being bastards peaking out through leaves in the bushes 1000m away to shoot you, versus a traditional FPS where you can shoot and battle people like a coked up machinegun toting gorilla multiple times within just a few minutes.