Your reply is merely speculation, that athletes would be willing to dope on the slimmest likelihood that it would be benefit them. It is speculation because doping has advanced far beyond a runner experimenting with arsenic in the 1908 London marathon.
Contrary to what you think, athletes do have a "menu" of drugs that can affect them in a variety of specific ways. These are developed medically with a high degree of scientific and pharmacological knowledge behind them. Doping is an industry - big business - with a high degree of expertise involved. Athletes typically are advised by doctors, trainers and coaches in what they use. They aren't speculating - as you are - they are applying methods that have been found to have worked. It has been officially estimated there are over a hundred illegal substances that are currently undetectable.
It has become child's play to effect improvements in strength, speed and stamina; the new frontier in doping is increasing the speed of neurophysical pathways improving mental speed, focus and agility, and genetic doping is seen as the prescription for the future.
The athletes dont have to know how any of this works, any more than you have to know how the drugs work that the doctor prescribes for your health - all you need to know is that in most cases you will get results - and medical conditions are harder to fix than to enhance basic physical attributes, as innumerable bodybuilders show.
If it was 1908 - or even the 1940's - I might agree with you, but comparatively speaking, when it comes to doping we long ago put a man on the moon.