Why do electricians, when working with electrical installations, stand on rubber mats or wear dielectric galoshes (boots)?

Why do electricians, when working with electrical installations, stand on rubber mats or wear dielectric galoshes (boots)? Is it enough to isolate a person from the ground to prevent electric shock?

Rubber mats and galoshes protect against electric current. since rubber is a good insulator and does not conduct electricity. It is not enough to isolate a person from the ground in order to completely eliminate electric shock.

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