The standardized rifleman optic used by darn near all militaries is some variant of medium range rifle scope, respectively being the Russian 1P86-1 and the American TA31RCO, something that can be both used in close engagements within 100m and further engagements past 300m. Training to use them gives an individual a more wider range of possible actions they can take in both conducting quick-reaction point-and-shoot drills and precise marksmanship as needed by the situation. With regards to practicality of use, it's superior to red dots because it allows for greater engagement distance which in turn allows the user to engage in distant ambush tactics and have both ample distance and time to withdraw from the area to avoid reprisal, which is overwhelmingly the most common and most practical form of asymmetric warfare that irregular forces engage in when faced with numerically and technologically superior forces. Red dot sights can only be calibrated to one set distance and can at best mildly hinder the user's combat capabilities if engaging in a varied distance firefight, red dot sights are fundamentally trapped in their niche specialization and encouraging to train exclusively in them is to trap yourself in a 100m box in the greater world of light infantry firefights. And falling back to my initial point, Iron sights usage is excellent training for gaining understanding of distance, learning visual range-finding, learning rifle zeroing calibration for engaging targets at varying distances, and ultimately as a weapon sight of last resort.