I think of that as a symptom not the cause. It's really death by a thousand cuts. We have exclusionary suburban focus zoning of the 1940s and 1950s , that bans or makes it impossible to build anything but single family housing in over 70% of residential zoned land. Preventing things like small mix used, boarding homes, hostels, duplex, triplexes, etc. Economic decline in large portions of the state's municipalities, shifting of job centers, disconnect between available stock and desired areas, car centric tourist development, bizantine building and safety codes. Rise in costs, etc. Speculative real estate markets and Airbnb are just another nail in the coffin of affordability.