Neutral is grounded to protect against earth faults and to eliminate transient voltages. If not earthed we would never know that a conductor has fallen down and during this if another conductor falls down ,the fault current will be 73.2 % more.With one conductor fallen on ground the voltage between healthy conductor and the ground will be 1.732 times the normal
Floating voltage- A voltage that is not connected by any conducting path (including resistors) to ground or the key voltage reference point
floating means no reference to anything
A system where the system ground is not actually connected to another circuit or to earth (though there may still be AC coupling) is often referred to as a floating ground