Climbers tend to look for ridge lines or consolidated areas for routes, terrain that is usually safer in terms of avalanche hazard. Generally they like to avoid wallowing on 30-40 powder bowls. They also are looking at slopes from a bottom-up perspective, while skiers are looking top-down, often at a roll-over. Skiers often do not follow their skin track down, so do not have first-hand experience with the slope that day. There are a number of factors that increase the risk for skiers in general. That's not to say there is plenty of risk for climbers, as the recent avalanche fatalities up on Mt. Wilson demonstrate. There is also a strong psychological component of skiing that can get people overly-excited to hit a slope that might be marginally safe. This can come from the euphoria of skiing, which can cause skiers to abandon rational thought in order to get more powder. It's amazing how different people behave after skiing a short section of really good snow.