Well, the reputation comes directly from a few big scandals in the past - Armstrong/US Postal most obviously. More generally, it’s obviously an ideal sport for

Well, the reputation comes directly from a few big scandals in the past - Armstrong/US Postal most obviously. More generally, it’s obviously an ideal sport for some forms of doping given it’s based around extreme endurance. But there’s probably also lots of doping in other appropriate sports - running has plenty of history, swimming, biathlon, cross-country skiing, etc.