What is the need for 3 different delays and 2 different compressors?

Note: On the "Pulse" tour, in-particular the "Comfortably Numb" video, there is a point which the camera is overhead and it shows Gilmour from behind along with his pedal board. The board seemed to be about 12 pedals wide and 4 pedals deep. Thats 48 pedals, is that even possible?lol