Answer: Simplicity. We have found that the client is not interested in researching exercises and workouts. They do not want to come to the gym to get on the computer.
With Custom Training they check in press one button and have the work out prescribed by their trainer. If you do not have a computer for your clients to access you can print the workouts for them.
Most people love not having to decide for themselves what to do at the gym. Having a trainer decide their daily workout has been the most liked feature of Custom Training.