Why? Because apparently they need some more incentive to keep units occupied. Also, even though a property might be vacant, there’s still imputed rental income there. Its owner is just receiving it in the form of enjoying the unit for himself instead of receiving an actual rent check from a tenant. That imputed rent ought to be taxed like any other income.
Do you have any info about this? Is it a tax on the value of vacant units, or a tax on the possible rental income of a vacant unit? I would like to read more about it. Can’t find much on Google.
It is called imputed rental value: https://www.taxolution.ch/swiss-tax-guide/imputed-rental-value/