I've fired a night qualifier every year for the past 20 years, and haven't had problems seeing my "night sites" after the first round.
First, every time I've shot at night, there was some sort of ambient light. If it was pitch black, you wouldn't know where to shoot. Second, most self defense type ammo has some sort of flash suppressant in with the powder. And finally, I don't own a carry gun without night sites. If they only give a slight advantage in a low light gun fight, that slight edge could be the difference between survival and burial.