Because fiber optic sights suck balls in low light, dim light and no light. I've used them in a dimly lit indoor range and they're worthless. Even at home if the lighting isn't ideal the fiber optic rods aren't visible. Indoors during the day with only natural light coming in through a window but no lights on in the room they've proven to be of little value to me. Pretty much only good for bright light conditions. They excel outdoors in bright sunlight. You actually need light to go through the fibers to get them to light up. The rods are also a bit fragile, and can break easily, but are easily replaceable on most sights, harder on others. My Mossberg shotgun has a fiberoptic front sight and it's broken once. At least it's easy to replace on that particular front sight. Just need a new rod, some wire cutters to trim it to fit and a lighter to secure it in place.
Also keep in mind regardless of whatever sights you go with for night sights, you 'll need a weapons light or flashlight. Can't shoot at what you can't see, and you should never be shooting blindly in the dark.
Also keep in mind regardless of whatever sights you go with for night sights, you 'll need a weapons light or flashlight. Can't shoot at what you can't see, and you should never be shooting blindly in the dark.

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