Simple truth: if you own a house, you would want house prices to go up, forever.

Hardly. I need a house. If my house price crashes to $5, I'll be able to get a much nicer one for $10. Just $5 extra investment.

The problem comes when you've borrowed against the house at the higher price. Negative equity is no joke, but I don't care what my house is worth otherwise. It's value is completely unavailable to me.