Tactical unintended discharge's.

[Mannlicher]

even cops should not point a gun until they are ready to shoot.  They are issued lights on their pistols?  Why?

[dogmush]

I took a citizens police academy course earlier this year. In one class they had the SWAT team to a demonstration room clearing exercise. Guns were not at low ready, they were up and ready to engage anything the muzzle swept. The rule of thumb is "You fight as you train." If you train to clear a room with the gun at high ready, it would be difficult to suddenly transition to clearing with the gun always at the low ready for the one time you're clearing a dark room with a weapon-mounted light.

They are doing it wrong.  They need retraining.

[Fly320s]

They are doing it wrong.  They need retraining.

even cops should not point a gun until they are ready to shoot.  They are issued lights on their pistols?  Why?

Because cops have different rules apparently.

My guess is because the cops are allowed/encouraged to physically dominate the environment by use of force.  Having a gun pointed at every perp in the room helps them achieve that domination.