Lasers run on batteries, which die at the most inopportune moments.
Lasers tell the bad guy in your home at 2am that you are A) armed, and b) your location. If he knows you are armed, he is more likely to use his gun.
All you've probably done at the range is practice with the laser. When the batteries die, you will not have the pratical experience of acquiring proper sight picture and alignment. The laser made you into a lazy shooter.