You can either enhance the athlete or the equipment, it just so happens that cycling involves more complex equipment attached to the athlete than most sports. I imagine this is even more of a concern in the Paralympics where various prosthetics, mobility equipment and other assistive technologies could give certain athletes unfair advantages.

The thing with Lance Armstrong popularized idea (especially in US) that cycling is exceptionally infested with cheating.

But there is doping even in curling.

Yes. The big tours had big cheating and the omerta going on for almost a hundred of years. And the never caught ex-dopers are now TV commentators or race managers.

Without illegal methods you wouldn't be able to perform at this level. Go watch "Icarus"