So far I have lived in areas with two massive RE declines. One in LA when farming and O&G imploded, the other here in GA more recently. A house, especially if someone needs to move, can be a weight of massive proportions. A house is somewhere to live, if you ultimately make a "profit" on it good for you. Most people do not track all the long term carrying costs of home ownership and if they did would come to the conclusion they lost money or broke even at best, especially if they love to renovate. Investing in public/liquid markets ensures someone can sell if/when they need to although it may be at a loss but then one gains tax benefits from losses in taxable accounts. RE is not like that unless someone is lucky, has well above RE knowledge or got a "family" deal reducing the purchase price of the house. If someone bought in a good area in ATL in 2010-2012 they would have to screw up royally to lose money, but that is an artifice of a massively depressed market making LT ownership much more appealing than in a normalized purchase environment.

I'm not against owning a personal residence, mine is worth less than 10% of my NW and it is nice and updated but far from palatial. Sometimes I really wish I had stayed in a condo that I was perfectly happy with that we acquired at 40% below market value from an estate, but the wife and dogs wouldn't have been happy. I have been pretty lucky with investment RE, but that could always change.

The 15 yr mortgage argument doesn't really hold water as a financially responsible buyer isn't going to overleverage themselves going in, and rates and HELOC/MTG qualification can change significantly in a short period of time with a negative impact on home prices. If a 15 yr mtg significantly impacts what one can save in tax advantaged accounts it would not be worth undertaking, either.