Whether for safety or operation, knowing when to ground is essential.
Wha'd ya mean?" says Bubba the plumber-recently-turned-heating-tech. "How come you're tellin' me I gotta ground that boiler ignition? I know better - my power saw works just fine without a ground, and it's bigger!"
Bubba's right about one thing. His saw does work without a ground. It might be better if it didn't because it's not safe. Bubba doesn't care about that one way or another.