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.
The storefronts being talked about are already zoned mixed use, it’s really just the first floor street side storefronts that are barren, with residential apartments 2nd floor on up.