You start off with absurdities, but you finish with good questions. I'll answer those latter with, "Well, maybe this time around, we can build sensibly!" Take Philadelphia, for instance. Or, Chicago. The nation's infrastructure stipulates that streets should be accessible to over-the-road trucks, about 72 feet long, about 10' 6" wide, and 13' 6" high. And, the streets should support those trucks weighing 80,000 pounds. However, both of the cities I've named have huge amounts of places where such trucks cannot go.
Maybe if we scrapped some of those ancient cities and towns, we could actually plan the new cities. Plans that not only accomodate those trucks that are required to navigate the cities, but plan in a lot of green spaces. Playgrounds, parks, nice wide boulevards, etc. Maybe we could have cities in which all structures are built to modern codes. Face it, 100 to 200 years ago, a lot of homes were little more than hovels. Those ancient homes are often times "valuable" today, simply because they have survived, and there are so many people needing homes.
How many structures in your favorite town are still wired with "widow maker" bare wires running through the attic, or behind the walls? How many should be condemned for the lead in the piping? How many have absolutely no fire safety built into them?
Maybe I shouldn't say that some of our cities NEED TO DIE, but there would be some pretty big benefits to be reaped from just starting over.