Why doesn't other areas in fallout's America have more modern buildings, guns and clothing

So I watched a video about Fallout 2 and I saw the Desert Eagle. A gun made in the 1980s. Why doesn't other fallout games have weapons that don't look like they're from the 1950s. Buildings in Boston as an example. Sanctuary Hills looks extremmely 1950s. Why can't it looks more modern? Clothing should look more modern aswell and why use combat armor instead of tactical vests? Combat armor is clunky and heavy but vests are light and isn't clunky. 

My question is why doesn't Fallout's civilizations modernize more? I know that's what people in the 1950s would think that's what the future would look like but wouldn't they modernize like what we did?