Field operations are expensive, so having all administration and resources in a centralized location reduces operational costs. Rather than three or four administrators or librarians in the decentralized training centers, for example, one or two can handle the work in the central office.
With everyone under one roof it is easier for people to communicate face-to-face. Staff meetings and conferences for educators are also easier as video links to field operations don't have to be set up. While being able to see other people on camera is possible, it still isn't the same as being there and discussing a training idea with someone over lunch.
Rather than being scattered between the central office and the field -- which require paperwork to organize and track materials -- having everything in one place means instructors can sign out resources as needed. So, for instance, a DVD can be used in one class in the morning and another in the afternoon. Having to send it in from the field might take a week.
Programs are easier to coordinate when everyone is under one roof. Rather than having someone spend an hour driving into the center to attend a training session on a new course, all instructors can easily meet. In conjunction with this, program coordinators can monitor classes and help instructors more readily than if they have to spend much of the day traveling to field operations.
Learners in centralized training centers can be assured that the courses they are taking meet the requirements of the training institution because they are closely monitored. Field operations may or may not adhere to the curriculum as closely as in-house classes.