Do people care about price to book value when they buy a stock? For a given stock on Google Finance, you won't find the price to book value shown anywhere on the page. On Yahoo's finance site, you have to scroll down the 12th page of info (titled 'Statistics') to find the P/B. It would seem P/B is not an important measure in investor's minds.
We can also see times when it looks like these stocks are great bargains. During the 1991 recession, they're all trading below book value, and in many cases with large margins of safety!
Also consider that these are the largest, most famous US homebuilders. Smaller builders may have less analyst coverage and so may represent bigger bargains!