It's 200+ years later. Survivors have spawned generations on generations of new human beings. Why are there still abandoned vehicles made of readily salvageable scrap metal laying around everywhere? Also, why little-no reconstruction?
Think of the scrap vehicles everywhere as being an alternative to scrap yards now, nobody is yanking it in and storing it all, so you don't see it in your day to day moseying right now. Imagine an earth quake strikes your hometown and 90% of the houses and vehicles become little more than piles of scrap - all the services to clean it up, and store it away are gone. Who's gonna do it?
Add hordes of Super Mutants, Raiders, scavengers, Rad Scorpions, Molerats, Yao Guai, Ghouls... they make it very hard to collect. Then remove probably 'all' craft expertise and skilled tradesmen engineers, plumbers, electricians, mechanics, carpenters, builders etc. from the picture, they all died either instantly or of old age two centuries ago and their expertise went with them, but perhaps a few passed on a little knowledge, but nowhere near like the skilled tradesmen taking two to to four year courses as apprentices after their sixteen/eighteen years of standard education.
It's pretty obvious why there is junk everywhere. Also, even in the homes of these people, if you've been raised in environment of 'getting by' with dirt, rust, and general crap strewn about the place, you're hardly likely to have a problem sleeping in a crap tip of rusty cans and mouldy carpets etc. You're hardly likely to let it get you down suddenly, go out and somehow salvage a vacuum cleaner and get busy dusting and cleaning. S'just not a priority when you're thirsty and hungry most of the time. Heh ha.