They may be wealthy countries, but they're also capitalist countries; that mindset optimizes for profits, for return on investment, for getting the most out of a workforce for the lowest cost.

Currently, and I'm not an economist so this is an armchair thing, I think two big factors are wage vs cost of living.

Minimum wage has not kept up with inflation or cost of living.

Job security has spiraled downwards, with employers preferring temporary, part-time or 0-hour/on-call contracts, or doing away with employees entirely and having temps or contractors instead (also looking at the gig economy here).

And cost of living has skyrocketed up, it was steadily increasing in the 2000's, and after recovering from the 2008 crisis they've gone up crazily. Additional factors in that are low interest rates, meaning that on the one side mortgages have record low interest rates and on the other low risk savings accounts have no interest anymore, so people are looking to invest. Given how the prices of housing have gone up because of these factors, people see buying a house as a great investment.

Anyway, all of these factors combined mean that fewer people can afford to live in a house, there's much more of the "working poor", etc etc etc.