I carried a light on my g19. Streamlight Tlr2s on my g19 when I carried 3/4 o’clock in a compact ctac holster. Surefire xc1 on my g19 aiwb in a Keepers holster. Having a light on your gun does not make it harder to conceal. I have changed my carry gun and do not carry a gun mounted light anymore. I always have a small flashlight on me, even when I had a light on my edc. It’s nice to have an extra light on you. NO you shouldn’t use it to look for the keys you dropped in the movie theater, but if you had to draw the gun and realized a light would be helpful in that situation it’s nice to have it right there and not have to break your grip to use it.
I dont know if I'd want one for an IWB Carry gun (my preferred carry method) but I have been looking into one for a bedside pistol. I'd be more inclined if there was a compact option but all the ones I've seen are still quite bulky.