They are largely based on police methods. Police will often announce themselves and everyone knows they are armed so surprise isn't as big a factor. If they are clearing a house, they may be using a carbine instead of a pistol so they need it to be weapons mounted. If they are using the pistol, they also need it to be weapons mounted so they can cuff the criminal when they catch him/her.
I rarely will need a light. It is rarely pitch dark in my house: between the street lights outside, the light I have on downstairs, and nightlights I have on the stairs, I can usually see people in my house (while my bedroom and upstairs is dark enough to maintain cover for me). I trained and regularly practice to shoot one-handed when I can't shoot two-handed (like if I decide I need the light). If I do need a light, I follow the technique taught by Chuck Taylor for decades (yes, equipment has changed, but this still works). Once you have identified your target, if you need to light him/her up, you can still hold your support hand with the flashlight under and wrapped around your shooting hand to give your shooting hand some additional support over just one-handed shooting. When I'm investigating, the light is off a bit to my side (so as not to show where my COM is), but if I have time to move to a shooting stance, it will be the one illustrated in the picture.
View attachment 1144205
I use a much smaller light than the one in the picture, but it still works with my little Surefire light. Not being attached to my weapon also means that I can use it for other needs as well.
Now, if you are invisioning clearing the house (in which case I'd be going downstairs), I can turn off the lights remotely, but I'm not clearing the house. I'm waiting upstairs and if they come up towards the bedrooms I'm protecting me, my roommate, and any possible guests. However, I'm following Chuck Taylor's advice here too... clearing a house is dangerous, I'm calling the police and leaving that to the professionals if I know someone is in my home. If I'm investigating a noise and realize then that they are already inside, well, we both have light to see since there are lights on on the main level of the house, so while not ideal, a portable or weapons mounted light won't be needed.
