My guess is two things: 1. Factory. Highly customised cars will require a very flexible workforce. Much easier to do by equipping each worker with a hololens

My guess is two things: 1. Factory. Highly customised cars will require a very flexible workforce. Much easier to do by equipping each worker with a hololens 2. Inside the car - turn all the flat surfaces into displays. No headmounting glasses needed. In a driverless car those big windows are ideal for projecting things onto.