Some societies degraded, or rather since everything was blown up, some societies had to start from scratch. While some may have been out of touch with the larger settlements, even Sulik from FO2 mentions he knows how to use a sub-machine gun(damned if I ever let him touch anything but a melee weapon though!). You work with what ya have! I'm do hope they bring back some tribal settlements though. It shows the contrast between how each group of people survive and flourish in this world.
That being said, I do love the new concept art. There is a sort of refinement and polish. I feel that some time has passed and people are beginning to find themselves and prosper once more. However, while others prosper, others may fall behind. When others fall behind, jealousy stirs, and shortly after, conflict. I have no doubt that their will be a mix of basic, even crude weapons, to the rustic traditional firearms that survived the past, the energy weapons that began to rise before and after the bombs fell, to whatever new and advanced arsenal that may come.
Mr. Serg, following my wall of text, am I reading too much into the pictures
?