IMHO the rates reflect the belief that the long term prospect of inflation in the US is very low and confidence that the dollar will remain strong..and the economy strong long term is good. I think this reflects underlying strength of US economy and belief by all investors that the US and the $ can't be beat..in the long run.
The realestate boom could be greatly reduced by raising tightening the credit requirements and drying up zero down loans.
In my area, homes average $300,000. Most young couples don't have $20,000 to $30,000 for a down payment. There's no low cost or affordable housing either.
I like to be optimistic about the economy. However, I am not certain how much longer the economy can continue to absorb out-of-control energy costs and not see a resurgence of inflation. Also, not to even mention the "R" word, in the past 35 years, every time the economy tanked, there was a higher energy component involved.