Re: Hostage situations...
Let's put ourselves in the cop's shoes. If you have a hostage situation, why do you think the hostage taker is going to come out alone and in plain sight to see what's up? He's either the dumbest hostage taker in the world and has unwittingly just let the hostages go, he's a hostage who's been released, or he's totally clueless as to what you're talking about and likely can't hear or understand the vague and often contradictory commands being given.
This is about training, bad training. They're taught to neutralize the any potential threat and then ask questions - maybe, collateral damage be damned.