Your iron sights should be co-witnessed with your red dot, so if the battery goes or you knock your optic about and it fails, you can keep on fighting without having to take it off.

iron sights rarely line up with a straight, hop-up tuned, trajectory. so a red dot dialed in to where your bbs go will be far from co-witnessed with iron sights. pointless if not RS

All my guns always were adjusted to use the irons. Either you don't know how to adjust yours or it's broken...