Everyone has their own reasons… as FSD pointed out some homes may have large equity stakes or even fully owned. In some cases these people think “well it will pick up again in the spring..” In other cases they get bad advice from friends or bullish real estate professionals… in other cases they may be just sitting and not paying their mortgage and letting the home slide away because they don’t want to go through a short sale and get hit with potential tax liabilities.
As Bugs said the RE machine will do all they can to combat common sense. They will build up a facade, they will have nice parties that Cyphire, myself and our kids will crash, and they will throw ALOT of money at all kinds of advertising media to counter the trend.
I gave up getting to wound up about it about 18 months ago because it will keep happening. Common sense is not so common when emotions get involved.