The perfect Zeiss Otus 85mm Lens subjects are people. An 85mm focal length results in a working distance that provides a portrait perspective similar to what you would commonly see when talking to someone with facial features not being distorted or overly-compressed. The f/1.4 aperture permits a shallow depth of field that removes background distractions. The incredible image quality this lens provides is the icing on the cake.
I'll contend that people are also the most valuable subjects available, both in terms of the value of those people and the returns available for photographing this subject. Finding paid gigs involving people is much easier than finding paid landscape, wildlife and other non-human subjects. Paid shoots are of course helpful in justifying the cost of this lens. Making portrait subject happy leads to great job satisfaction.