I'm not a fan of flip-up iron sights that clamp on an accessory rail, either, BUT...
... But I don't want to own two AR-pattern rifles, one with the carry handle and fixed iron sights, and another flat-top for shooting with optics.
Having one gun that's a flat-top and can be fitted with any kind of sighting option (irons, red dot, magnifying scope...) is just more practical.
And if you're going to shoot with a real scope cranked up to 4X or better and expecting good accuracy out to a few hundred yards, you'll want your scope mounted nice and low, not perched on top of a 3" high pedestal.
... But I don't want to own two AR-pattern rifles, one with the carry handle and fixed iron sights, and another flat-top for shooting with optics.
Having one gun that's a flat-top and can be fitted with any kind of sighting option (irons, red dot, magnifying scope...) is just more practical.
And if you're going to shoot with a real scope cranked up to 4X or better and expecting good accuracy out to a few hundred yards, you'll want your scope mounted nice and low, not perched on top of a 3" high pedestal.