Well name me other sports where young guys aged 22 or younger are encouraged to not compete because doing so could ruin their careers.
In all the big mainstream sports, people in their early 20's or even teens have a big presence. So forget about those.
Marathon, often touted as the hardest sport by people who dont know much about road cycling, has young guys around that age competing and winning. Hell Sami Wanjiru was 21 when he won the olympic marathon 2 years ago. The London marathon was just won by a 23 year old. Triathlon, a sport which people say is the hardest because they have to carry the extra upperbody muscle for swimming. Current world champion Allistair Brownlee was 21 when he won it last year.
But in this thing of ours, never mind competing, people around this age are prevented by their teams from even riding grand tours because it would ruin their careers. It is just too tough.
I know Rabobank for a fact don't let 20 year old neo pro's ride even 1 grand tour. They protected Gesink and Mollema from riding them in their first year.
Probably better than burning young guns up. I remember Spilak two years ago was used in so many races he was complety gone after may and needed 1,5 year to get back at his old level (and winning Romandy this year)
And peter sagan. Any other sport he would have been pushed straight to the top by now. He might ride the flat days of the Vuelta as prep for the World Champs (im not sure) but as far as completing a gt goes. Forget about it.
Also what other sport so much impacts the anatomy. Weve all seen the horror pictures of Rasmusen and others. The ammount of weight the cyclists lose over the course of a grand tour has got to be big.
And then there is the hct level. A grand tour lowers the ammount of red blood cells in the body, far more significantly than any other sport.
You could argue the boxing impacts the anatomy with scars and injuries, but cycling has injuries too, bad ones, and in boxing, the refs are there to stop fights if they get out of hand.
There are probably some other variables in the body which are impacted by riding a grand tour which i havent even mentioned.
And this is just the grand tour aspect of road cycling. What about the 1 dayers, and the very difficult 7 day stage races.