I've found something annoying regarding sleep too, I used to see my sims doing woohoo and then sleeping in the same bed if their energy bar were medium or low, the problem is that they play the sleep animation but are not really sleeping, they lack the action that shows how much time they will sleep, and the energy keeps draining along with hunger and bladder. They won't wake up unless I click a small icon that shows up at the botton of their action bar ( like the sticky man who is sitting when they use a chair ) or if I command them to sleep, then they'll wake up, and go to bed again and rest.
