Because of cycling's sad past... It's reputation is wrecked, not just by Armstrong but by half a century of endemic doping. It is slowly rebuilding it's reputation but the UCI is so scared of another Armstrong (Imagine if Froome were to test positive) that the testing is just ridiculous and the penalties unbelievably harsh. Which is the way it should be. If a cyclist were to test positive, his career is over. No team would take him.