Back in the last huge price increase of the 70's & hearing & watching the going's on as single family homes without basement apartments were the norm.
Going to School with kids who had relatives in Europe who were looking for investment places around the world to park their cash. 
We watched as that Europe cash came here & was hidden from the gov't back then as locals bought homes for their European relatives. 
Real estate agents put in thousands of illegal apartments to help drive up the prices.
We knew we would have little chance to afford a single family home without paying off a huge mortgage.
Municipalities are partly to blame as well as they still today say there's 2 parking places per home but 1 of those includes the garage spot leaving no room for the basement apartment peeps except on the street.
Commercial & Industrial lands are also a problem as Mom & Pop places are almost non existent these days compared to back then as well.
This also caused the Mom latch key kid problem.