You don't even need a night qualification prior to commencing your CPL course, however if you don't have one it needs to be incorporated into the course and CPL instructors are invariably a lot more expensive than PPL instructors who would usually do a night qualification.
Flying schools can attach whatever conditions they like to you hiring their aircraft, and it's probably related in some way to the fact that the FAA PPL includes night privileges as part of the basic license. Why they should think you unsafe without such an endorsement when you have no plans to fly after dark is a little bemusing.