Don’t discount how rare 20% price drops in housing are historically - a nationwide 20% price decline has only happened once since 1951 (where I could find statistics start) and even then would only have applied for purchases in a 1 year window. House prices are historically high across almost any metric you choose right now, so we could see another incident of that, but it’s also possible we could see real house prices depreciate with inflation while holding nominal value.
Homes are massive, illiquid assets with high transaction costs and (unless you have many of them) are poorly diversified. I'd even argue it makes more sense to look at a primary home as a forced savings plan rather than as an investment.
I disagree. It’s too big a chunk of people’s net worth to not analyze like a financial investment, if only to make one stop and think about them opportunity cost of buying at various price points and how much you are really spending to consume living in a nicer house (because there is definitely a consumption angle.)
A primary residence even makes a good component of diversified portfolio so long as it is not the sole or dominant aspect of that portfolio.
I understand your point about it being a "forced savings plan", but with 5-10x leverage on most loans even a housing market that appreciates at inflation can provide significant returns (or losses) in the long run.
On the other hand, it probably reduces risk to take the 15 year loan if you can afford the payments, in order to more aggressively build home equity and shield yourself from a sudden shock/downturn. If rates shoot up after, say, 5 years (and home values drop 20%), someone who's made 5 years of payments on a 30 year loan will be way underwater, whereas someone who's made 5 years of payments on a 15 year loan still has positive equity.