What do you consider low density? I really don't like the idea of stamping out all single family homes and nice green areas in proximity to cities. Mixing high density in with commercial areas seems fine though.
What is the benefit/cost ratio of 2-3 story houses vs 10 story housing vs 20 vs 30 vs 40?
Houses are for families with kids right? What do kids want? Kids want other kids to play with. Kids want to attend classes and learn stuff. The more options a kid has, the better.
Which area has more kids and therefore classes: low, medium or high density areas?
I understand that there is a trade-off where we don't want 100-story skyscrapers but to me, single family homes are an infrastructure luxury that hasn't been thought through and something we'd benefit from re-considering and re-educating people about.
-More natural settings shown to improve mental health
-"neighborliness" scales inversely with density to a point - less neighbors means you're more likely to get to know them, while with more people there are too many so the crowd of people gets depersonalized to a degree, because 50 neighbors are too many to keep track of.
-you don't have to go to some crowded city park full of garbage when friends have yards with their own stuff like sandboxes where they can have some privacy from for example sheltered city people or park cops freaking out over the kids having nerf guns
-other activities become more feasible like bike riding (I wouldn't feel good letting a kod bike around NYC), ATV's, fishing
-more outdoors setting prevents aesthma
-safer setting for the kids overall
Your concerns just don't work oout that way in my experience. I was in single-home-only towns as a kid and there was no problem playing with neighbors or anything. Even when houses are a mile apart it's really not a big deal just being driven to them.
And since when do kids want to attend classes?
The benefit/cost ratio is what makes this conversation worth having.
From an environmental perspective there is no contest between single family suburban development (aka sprawl) and dense urban living with plenty of parks.
Also, you won't find bigger bike/transit activists than the people advocating for the abolishment of single family zoning.
I don't think anyone seriously wants to replace every single family home with something more dense (even if the rhetoric indicates so). It's harmful and unnecessary. E.g.:
* There is an estimated 3-4 million housing unit deficit in CA, on 14 million total units (US Census). We'll take 4 million units to err on the extreme case.
* CA currently has 7 million single-family homes (US Census)
* Assuming 100% of that deficit is made from replacing a single family home with a quadplex, it would take 1.3 million single homes -> quadplexes to make up the 4 million unit deficit.
Even in that most extreme case, I can't imagine one quadplex per block would affect green areas or the totally legitimate choice to live a single family home.
In reality, I think most YIMBY advocates want mixed-use medium density, which requires an order of magnitude fewer buildings.