IMO, the main reason is because real estate prices are ridiculously over inflated.
Locally here in Montgomery County, Maryland I drive by new construction sites of plain brown-wrapper townhouses that are less that 18ft in width with signs touting "...from the HIGH $400K's" No facade porticos...no brick...no garages...
They should be half that.
Home with 5,000sqft of LA (Living Area) I sold for $610K less than a decade ago now has a market price of $1.4M
GTFOH!!!