Is ground connection in home electrical system really necessary?
What you are not considering is that an earthed chassis or metal box containing a &quot;rogue&quot; live connection will be self-revealing should a fault occur that causes live to touch the earthed metal. It will blow a fuse and within a few milliseconds the problem is made safe and revealed.
For an isolated AC source (such as the secondary of an isolation transformer), there is nothing to reveal that live may have come into contact with the metal box. You can touch it and maybe receive a small tingle but, it isn't clearly self-revealing.
Fault 1 has occurred and it is not self-revealing...
Some time later, another fault occurs that can be anywhere on your street and in any of the houses on that street. That fault causes neutral to become connected to earth.
Fault 2 won't self-reveal either because it won't blow a fuse: -
Then you touch the unearthed metal box or chassis: -



simulate this circuit &ndash; Schematic created using CircuitLab
The magenta arrows show the flow of electrocution current
Now, the metal box is a death trap (because it isn't earthed) and is awaiting the next unlucky person to come along and touch it. Nothing has revealed itself that tells you a dangerous situation has arisen.
The first &quot;hint&quot; (if you survive the hint) is electrocution.