It actually is. Rents are expensive because zoning laws severely limit density and require lots of car parking.
Maybe you've got some good examples from other countries, but here in the US the only major city with reasonable zoning is Houston which has quite affordable homes.
I'm not sure what happened to them, but there was a startup trying to do this: https://www.curbed.com/2021/03/brownstone-shared-housing.htm...
SROs, residential hotels, boarding houses and the like were all banned in the 1950s (and the surviving ones dismantled through the 1980s), a loss of about 100,000 units of affordable housing.
Consider this lovely e-book for further reading: https://publishing.cdlib.org/ucpressebooks/view?docId=ft6j49...
Or this lovely Simon and Garfunkel song about the NYC homeless on the streets of SoHo, contemporary to that era. https://www.youtube.com/watch?v=PCVnPIE3juc
If we just respected property owner's rights to do as they see fit we wouldn't have these problems or not nearly to the same extent.