In 1910 the Tour had a stage that finished on top of the Col du Tourmalet. That stage was a stupid 326 kilometers long and covered 7 mountain peaks. On gravel roads. With single speed bicycles that weighed 40 pounds and flatted regularly. Octave Lapize (who would go on to win that stage, and the Tour overall) famously screamed at the race organizers as he neared the finish line "You are murderers! Yes, murderers". The newspapers loved it, and that particular route is still known as "The Circle of Death".*
Cycling is a sport of attrition. Grand Tour cycling in particular. The winner is the man who can hurt the most without slowing down, plain and simple. It's a sport of gruesome pain, and the insane embracement of it.
*what did the sport do to commemorate his manic meltdown? oh, they put a statue up on the climb of him suffering excruciatingly as a reminder of what a bike race is like.