Why don't RVs need an earth ground for AC circuits

This is NOT to answer your question, but it might interest you.

Navy combat ships do NOT ground any system. The reason
is that, with our 'normal' HOUSEHOLD grounded systems, if the HOT
wire touches ground the breaker trips or the fuse blows. In combat,
this is obviously NOT acceptable !............in place of the grounded
system, a GROUND DETECT system is used to detect grounds, and they
are removed as soon as possible.

I have long thought that this should be extended to homes and businesses.