More advanced skiers take greater risks, bigger falls, and are covering more terrain.
Beginners are usually extremely conservative in comparison with more experienced skiers.
Finally, you should be most fearful of other people, and their recklessness. You cannot control what other people on the mountain are doing, and as ski areas become increasingly more crowded, you are at a higher risk of being hit by another skier. You don't have control of other skiers on the slope. People who choose to take safety precautions tend to be more safety conscious, in general. It is not likely when you put on your seatbelt that you will drive recklessly - the same cause and effect relationship goes for helmets.