1. We actually do not have a market mechanic that exists in the United States that allows people to choose properly dense homes or neighborhoods because of a number of reasons. Search tools and things like that focus on metrics like square footage or number of bathrooms, and so people select for that "bigger is better" "more is better".
2. State departments of highways (they don't do anything besides that in most states) consist of individuals and contractor companies who have become adept and normal with building highways, and so all of the organizational inertia is on building anything that looks like a highway for the safety of drivers, to the detriment of everyone else. Since only highways get funded and built in most of the country, we end up having other companies like fast-food restaurants build in ways that cater to the driving demographic.