In practice, the primary desire to not have spill is for combat/combat-like scenarios where you don't want to illuminate your position, or your buddies' positions to your sides, etc.
That is a valid concern, and there are lights that are best suited to this role.
OTHER than that, there is no real advantage to having to view a large room a little at a time through the moral equivalent of a paper towel tube.
IE: If there IS some guy hiding, and you are sweeping the light all over, not knowing if anyone is there or not...if he IS there, he SEES your little patch of light sweeping around, and, knows when to duck when he sees its coming towards him.
He can shoot you while you are doing all this if he's armed of course.
Additionally, in real life, if using a flood light, you have light beyond the "cover" anyway...its more like you flipped on the light switch and its daylight.
If you still had a narrow beamed spot light with too much power for the range, sure, you'd get bounce back/glare...but the POINT of a floody beam to is give a wider, more diffuse lighting of the area, which DOESN'T, in practice, cause these problems.
So, for some of the dogma that's out there, much of it was provided in TRAINING, training designed and/or sponsored by those with a vested interest in people BELIEVING that 100 lumens is more than enough, no matter what, etc.
The 3D LED Maglight for example is ~ 131 lumens, but throws ~ 364 meters. If you use one because it was issued, etc...you cannot see much at a time...you are playing "connect the dots" with the light, trying to stitch together a picture of what's out there.
The little patch of light is all you see out there, you are blind to what lays in the dark periphery.
If you were instead issued a Surefire Fury, it has a nice floody beam that still has throw to it...and you could see some of the periphery/search more at a time/give the other guy less time to shoot you, etc.
If the guy was 300+ meters away, and prone, etc, you may or may not be able to pick him out from the scrub, etc with the Fury, even if the diffuse light reaches that far....there may not be enough Lux.
If you had a Fenix TK70/SF Hellfire HID, etc..., you would see the guy, and the guys in wait to his sides as well, and take in the entire field/positions as soon as you flipped the lights on...and if the guys out there have weapons trained, you then know to flip the lights back out pronto....
As opposed to them picking you off while your narrow beam looked at all the empty areas.