It is a common misconception that because neutral and AC ground are bonded together at some point and also read as a short when tested, that the two are functionally equivalent and interchangeable. Wrong! Neutral is a current carrying conductor in an AC circuit - the ground is not. For example, lets say a properly AC grounded power amp is under load and is drawing 10 amps from the AC source. If you measured the current in the amplifier's AC cable hot wire it would be 10 amps (no surprise) but the neutral would also read 10 amps. This is not a total of 20 amps. It is10 amps flowing through the entire circuit made up of the AC power source through the hot wire through the amplifier's power supply and back to the power source via the neutral. Current in the amplifier's AC ground wire should read zero amps. If there is current flowing in the ground wire there is good chance the amplifier or the electrical wiring has a problem.
In many portable AC systems in Europe and the UK built to electrical code with ground fault detection, if there is as little as 5 milli-amps of current flowing in the ground, the entire system will shut down because it sees this as a ground fault and an electrical hazard. Current flowing in the AC ground bus is detected by the Ground Fault Interrupt circuit and seen as a fault condition. This triggers either a local branch or a system-wide shutdown depending on the design of the AC system. For examples of current draw you can relate to, a regular sized red LED draws about 15 milli-amps or a typical piece of rack mounted audio processing gear like a solid state dual gate or compressor is fused at around 250 milli-amps or a maximum 1/4 of an amp at 120 Volts. Those fault protected systems detect this condition the same way as our GFI (Ground Fault Interrupt) AC outlets you see in bathrooms which are designed to keep people from being electrocuted when things like hairdryers accidentally get dropped into the bathtub or sink.
AC/Earth ground is a safety AND a reference.