The Flight Attendants don't have any control over the temperature except to ask the Pilots to regulate it. At least not on Alaska Airlines airplanes. I know it's different on some of other airplanes at other airlines but the cabin temperature controls are in the cockpit. That said, I think the general rule is to keep it warmer at night because people do sleep and as people sleep they seem to get cooler easier. Since we don't offer pillows and blankets the best we can do is try to keep the cabin slightly warm so people aren't uncomfortable. it has nothing to do with not wanting to serve the passengers. Unfortunately, it's not easy to make every person happy. I prefer it to be more on the cool side myself but late at night I think the majority prefer the cabin to be on the slightly warmer side.