It depends on the game. For something like COD, it feels like it goes against the fast-paced nature of the game. However, in squad-based games like Battlefield it's a sensible tactic. You want to observe your surroundings and do some overwatch rather than running in guns blazing. (However if you're just sitting on a hill sniping other snipers for 30 minutes rather than playing the objective it can be annoying).