The ground conductors must be bonded to neutral at the service entrance. Otherwise you risk having neutral at one voltage and ground at another with high impedance between. In the event of a short to chassis the return current to neutral (perhaps up a pole or on a transformer pad) will be through the top soil which is high impedance, preventing it from working to trip breakers and fuses, leaving a potentially lethal voltage at the chassis.
By bonding ground and neutral at the service entrance you ensure a low impedance return to ground and if a short occurs increase the chance of tripping the breaker before melting a wire and starting a fire.
50 years ago netural was used as a way to ground chassis (the outer metal envelope of appliances) and experience taught us this was bad because neutral carries current, and when that current flows through a bad connection it raises the voltage on the neutral.
The ground wires may go bad, but they should not be carrying current except on an unexpected short, therefore the ground conductors remain at near 0 volts at all times except when a short occurs.
The formula V = I(current) * R(esistance) will help here. If I is 0, then V must be 0 even if R is high. That’s the normal state for the ground wire across your entire home.
Neutral often has current anytime you turn a switch on. Say 10A. Now 10A * R means V is not zero. If you tie that to the outside of your amplifier, you now have an AC voltage you can touch!
This is why 2-wire electrical construction is prohibited today.