try living in one. they are great maybe from age 24-29. they typically cost more than a mortgage in my area. you don't talk to people when you are that close. I find the greater the distance between neighbors the better the relationship.
I also see a lot better community with less people, and I'm sure there are many reasons for that.
Which isn't to say anybody should be forced into a multi-unit building and mixed-use neighborhoods. But as you point out, prices for these types of settings are often higher than detached homes, indicating that they are under supplied and more people want them then are currently allowed to live in them.