Small magnified optics have been around and recognized as a logical next step for combat rifles as far back as the Second World War. The German ZF4 and Colt 4x demonstrate that 4x magnification seems to be the sweet spot as it provides enough zoom to be useful at expected combat distances (300 meters) but not so much as to become unusable closer in.

The bottleneck had primarily been manufacturing enough quality optics to be mass issued and the idea that most troops couldn't shoot well enough to justify the additional cost. The first is largely a thing of the past with such available options like the Primary Arms microprisms and the second is just a training issue.

Yes, you should know how to shoot with irons as it builds your understanding of how marksmanship actually works but put an optic on your rifle if you actually plan on using it on a two way range.