It is absolutely financially viable to sell or rent a space that is receiving 0 income otherwise. It's just not what they want.

The places don't need lots of work to turn into apartments. They need lots of work to turn into lots of apartments.

There is a point between "leave it almost as is and rent out as many units as there are existing bathrooms" and an extreme retrofit to maximize the number of units that becomes worth it. The former scenario is still better than getting nothing.