Why are you advised to wear rubber slippers or shoes when handling electrical applianceswhy?

Rubber, or other insulating soles, are advised as the last defense against electric shock when working with hazardous voltages. They help to prevent a path to earth and so limit current passing through a body if there is contact with high voltages. It is the last defense because careful workers will always ensure that power supplies are turned off, disabled and protected against tampering as well as physical checks for mains being present.

Note that these precautions are for work with mains wiring systems and not for day to day use of household appliances. Domestic electrical equipment is designed and built to be safe in normal use, with or without rubber shoes.