True! Which is why it is so difficult to understand why so many BA cabin crew feel that shopping on a layover, particularly in North America, is so much more important than planning their rest properly during that layover. The resulting moans about tiredness et al on the return journey just don't cut the mustard, do they?
Are you suggesting that we should stay in our rooms for 24 hours instead? Maybe it's the tiredness of flying back and forth (like going to ORD, BOS, DEL and YVR in 18 days total) that makes you tired and not that you are out shopping instead of planning your rest? It's not always possible to sleep, or rest, because of jetlag.