Highly unlikely that 10,000 landlords with an extraordinary desire to maximize their return are being "irrational". If you rent out the property in San Francisco, you effectively lose control of what you can do with it. By not renting it out, you maintain control, and you can rent to family, make use of it yourself. I'm guessing that airbnb also is an attractive option now to get around the price-control laws.
<cynical thought>
But I suspect renting it to family/AirBnB - and not declaring the income - ends up looking very much like "leaving the building vacant" on official records...
If you rent out property for residential use anywhere in the US, you do lose control of what you can do with it, outside the bounds of your leasing agreement and local law regarding the topic.
Most jurisdictions recognize the need for a person to have a safe, personal, private space in order to have a happy and productive life. It is a recognition of this fact that causes most places to agree that a man's home is his castle, even if he is renting his home from another.
