Why keep a dog and bark yourself

Don't do a chore that should be done by someone you hired to do it. A literal example of the expression would be a home owner who buys, trains, and maintains a guard dog, but stays up all night in case of intruders. Jonathan Swift in Polite Conversation wrote this exchange between a woman of quality and her servant: “‘Good Miss, stir the Fire.' ‘Indeed your Ladyship could have stirr'd it much better.' [To which the woman replied] ‘I won't keep a Dog and bark myself.'”