As part of the air brake pre-trip check, why should a driver let air pressure build to the normal range before testing?

During the air brake pre-trip, the driver should let air pressure BUILD to the normal operating range (about 100-125 psi) before performing the brake tests, because: the brakes need adequate air to operate properly; and several checks require a fully charged system first — the GOVERNOR CUT-OUT test (verify the compressor stops pumping at ~125 psi), the LEAKAGE tests (start from a known full pressure to measure the drop), and to verify the LOW-AIR WARNING activates as pressure is then drawn down (~60 psi) and the SPRING BRAKES apply (~20-45 psi). CDL air brakes inspection. The full pre-trip air check sequence builds pressure, then systematically tests build-up rate, governor, leakage (static and applied), low-air warning, spring brake application, and functional service/parking brakes. Knowing why the system must be charged before testing is commonly tested.