In Britain, cab drivers make 65,000 British pounds (the equivalent of $100,000) a year. That is enough to make one would-be cabbie give up his business as an engineer to spend more than a quarter million US Dollars and four years of his life in order to become a cab driver.
Meanwhile, Doctors working as general practitioners in the UK start at 23 thousand pounds, and max out at 65 thousand. The average pay for a cabbie is the same as the top pay for most doctors. So where do you think the brightest and most talented people are going? Certainly not into the medical profession.
That is what happens when you attempt to thwart market forces by intervening with government licenses and restrictions.