At least in the US there are more people who want to be doctors than positions available. The bottleneck is medical school acceptance rates. To practice medicin

At least in the US there are more people who want to be doctors than positions available. The bottleneck is medical school acceptance rates. To practice medicine you need a medical license, which you can only get from an accredited university. I knew students who were rejected from medical school, but I also knew far more students who were at one time pre-med, saw how much effort and debt that would-be doctors would need to take on, and saw the risk of pursuing an e.g. biology degree where their entire future hinges on getting into med school, and they chose a different field.