Why it is difficult to go beyond medical entrance exam?

Why it is difficult to go beyond medical entrance exam?
Because medical school is highly challenging. We wouldn't want only just any old soul giving us medical treatment. We want someone who is smart, able to distribute an accurate diagnosis, and able to integer out how to treat our illnesses.
Because the more people who fall through the less doctors in attendance will be; and then more doctors will be within demand and we know what happen when things are in emergency.
or, on the other hand, I don`t know they just want with the sole purpose super nerdy people to become doctors. You wouldn't want someone beside an IQ of 50 to practice heart transplant surgery on you.
Because it needs to be to weed out the inhabitants who don't have the intelligence to become a doctor. No one wishes to go the worst doctor. They want the best doctor.