And there are good reasons (and bad ones) for their popularity.
This is helpful, as your eye wants to focus on the target.
It also makes it easier to observe the target, which in a defensive scenario is extremely important.
The attacker could move, could surrender or could initiate some motion that requires you to react.
Most criminal attacks especially those outside the home occur at very close range.
Were talking inside of three feet.
Criminals dont yell Im mugging you!
You may be forced to shoot from retention, which means not using your sights.
Important Perspective
Also, the dot itself can serve as a warning.
Thanks to Hollywood, everyone knows what a little red (or green) dot means.
It could make an attacker rethink his life choices, or at least his victim-selection process.
I wouldnt rely on that deterrent, but it does exist.
Some will argue that the laser gives away your position.
However, its not likely something to worry about when defending yourself against a common criminal.
The utility
First, merely attaching a laser wont help you hit the target.
The laser needs to be zeroed to your pistol, and, more importantly, for the correct position.
If it is zeroed so your front sight blocks it, much of its efficacy disappears.
Rather, a laser is a complementary advantage that works in tandem with your handguns sights.
Think of it like all of the great new safety additions to cars.
That means that the point of impact will be right on the dot of the laser at 35 feet.