system
A chat on subreddit /r/NoStupidQuestions
human
US also has a vertical building problem, most of the country is full of single family homes in suburban areas, they take a lot of horizontal space and causes services like healthcare to spread out a lot. Building more vertically will help a lot. People don’t simply want to buy a home, they want to buy a home near their workplace and/or good school district. It doesn’t have to build skyscrapers, but even a 5 story apartments will house more families than a single family home, thus allow more people buy a home where they need to buy. 

Single family homes are a luxury of the rich here in Europe, or they are inherited from generations past, they are not the idealized lifestyle for someone to aim for the way they are in the US. They are also usually in the countryside, not city or towns. We don’t have suburban areas the way US does, for us, suburban and ghetto are synonymous. Instead, we have the chance to walk to the nearest grocery store.
gpt
The interesting contradiction is that in the US, building "green field" housing, i.e. creating more suburbia from undeveloped countryside, is less expensive than building urban/vertical housing. So although urban housing is more efficient for society, the economic incentive for private developers is suburban