As players, we've got no objection to exploring a world we simply cannot significantly influence. If the enemy doesn't see sneaking on him from behind or his side, then they can not cry in the market to alert his comrades nor will he have a very chance to fire his weapon. Of course, like with perfect story telling, Flynn double crosses Drake as soon as the they get their hands on the oil lamp and instead gives off Drake to handle the security officers on his own.