First thing I thought of was all it takes is one person not wearing it to gain an advantage and everyone else will follow.

This is a sport where people take EPO to increase red blood cells and it thickens to blood so much it can cause heart disease, stroke, and cerebral or pulmonary embolism. They voluntarily train for a 21 day torture test totaling ~3500km going up mountains and at the end look like survivors of famine.

If they could remove some organs and add a third lung with a 50% chance of survival, they'd do it.