Because it is one of the most difficult sports, if not the most difficult one. There are not many others, where you race 4 to 7 hours 6 days a week (and besides

Because it is one of the most difficult sports, if not the most difficult one. There are not many others, where you race 4 to 7 hours 6 days a week (and besides the 3 main tours, you are engaged in a gazillion of one-week tours, 3-days races, one-day classics, etc., teams run several races happening at the same time in different part of world, even second or third categories teams). Another parameter is that it is probably the sport where it is harder to make a difference, because of the importance of drafting. Leaving the protection from the wind at fair speed is a bit like hitting a wall, it requires an amazing amount of energy compared to staying in the group. But if you ever want to win, at some point...