[CitrusFruits]

The article mentions a lot of the reasons. Our building codes, especially the double stairway requirement, eliminate a lot of reasonable layouts and have downstream effects on the economics of apartment buildings. Another reason that isn't mentioned in the article is that there are different ideals for family housing, especially in suburban areas like Walnut Creek. Family apartments just aren't as desirable.

[throwway120385]

Family apartments could be really desirable, but nobody builds them because of the building codes so people don't look for them. The point that a single-family home costs 1.5 million dollars is very applicable here, as the monthly payment on that loan is cripplingly expensive or totally out of reach. A 4-bedroom apartment for a family of 4 would be extremely desirable in that market.

[bluGill]

While building codes are different, those are not different enough to explain the difference. I've seen plenty of people try to propose layouts for apartment buildings that would meet the U.S. requirements and be much cheaper, but no one builds them, even though they should be legal.

The real problem is families in the US don't desire apartments and so no one builds apartments that families would desire to live in, thus perpetuating the problem.