I don't know why people keep saying that you aren't supposed to use the weapon mounted light to search. All I can figure is that they have one of those old sheetmetal body, plastic cap, C celled Ray-O-Vac battery flaslighted from the 1960s still on their guns that only shine about 30 feet and the dim yellow light doesn't light up much outside of the central hot spot such that if mounted on a gun, you have to point the gun at what you want to see.
Here in the 21st century, you can light up an entire room with a tiny light pointed at the ground, such as with my rifle mounted light with the rifle carried in low ready or pistol mounted light carried similarly. The lights have enough splash outside of the core beam that I can brightly light up a target without pointing at the target.
If you have the gun anyway, why not have a light on it? Nobody says you have to use it. You can still use another light if you so choose, but as Constantine said, having a weapon mounted light gives you a free hand. You can use that free hand for all sorts of things like dialing 911, securing or opening a door, guiding a loved one to safety, staunching the flow of blood, clearing a malfunction in a gun, etc. Tap-rack gets really squirrely when you try to do it when a flashlight in your hand, even more so if your hand is wet.