Scenario: You are facing an enemy tank. You peek/poke from cover and get shot. You say "OH CRAP!" and pull back into cover.
Time and time again, I see this scenario. You already messed up and took damage. Pull forward, make an aimed shot and deal damage, then pull back into cover.
Obviously, this does not apply in some situations: 1) Against an autoloader, 2) Against a tank with a fast reload, 3) When there may be other enemies to shoot at you, etc.