The analogy you make is helpful, but it immediately brings attention to one thing: you generally don' invite "someone in a cordial but not really friends relationship with a family member" to stay with you all the time, day and night. People you do let stay with you are people whom you either trust, or expect to trust as the relationship develops. There's no relationship development with an Echo - it's forever an agent of a faceless corporation that's indifferent to you.