Basically it's because of how the divisions began a long time ago, there was production which was unmodified off the shelf guns, and open which was heavily modified with a compensator, then in the middle you have limited which is modified guns. Limited and open were and are still basically built around the double stack 1911. Limited and open had major scoring so people ran 40 or whatever. They have changed the division rules a bit, now you can modify a production gun quite a bit, just not to single action because then it would be impinging on limited. Them when optics come out, they make carry optics as "production optics" and let you have extended magazines so everyone started shooting that instead, then made limited optics and dropped major scoring because it's dumb. It's basically because people would whine if they just combined divisions even though the majority would be fine with combining carry optics and limited optics, but as you have probably learned the gun world is filled with cranky old men. But they can avoid that by instead just creating a new division and the old division still exists but no one shoots it. I don't think I've seen but maybe one guy shoot limited ever, a few single stack here and there but iron sights are pretty rare. I don't even have anything without a red dot anymore because it's so much better to just use a dot. Like I said it won't matter in the beginning because you won't be competitive, but it wouldn't be the worst idea to get it milled for an optic because that will immediately make you more competitive. It's basically do you want to line up two blurry iron sights with a target or alight one red dot with a target. You want to be pulling the trigger as soon as you are on target.
