Why services that need to receive a signal, like Bluetooth or GPS, drain cell-phone battery?
Receivers are very much active devices that require energy to operate.

Modern Bluetooth receivers require very little energy to operate in receive mode. They should usually use a small percentage of the energy used by a cellphone in typical use.

GPS can use a significant percentage of total energy used.
Active GPS tracking is a high energy application. A GPS receiver is more complex than either broadcast, FM band or even cell-phone band equipment. Energy use does not directly scale with complexity (fortunately) but a GPS receiver needs to receive multiple satellite signals simultaneously and analyse the results to produce position, velocity time and other outputs.

A good idea of relative energy use can be obtained from your phone's records.
In Samsung Android 5.x see "settings - more - battery"