Simple argument is that being a doctor usually requires passion in helping people. That's true, then again many people study medicine for different reasons.
To become a hedge fund manager you can set this up at home, you can study actuarial science at uni for 3-4 years and still land a job in the city. It's guaranteed you'll be making a stable income between 50k-100k within 2 years because of market fluctuations.
People saying that your job will not be stable are lying to theirselves. With that experience you can literally transfer into any kind of employment across the world.
I don't like seeing the sight of people's blood, dealing with infectious people unless it's someone close to me. If you want to be a doctor fair enough - don't stop yourself. I encourage more doctors anyway to start from here.
I don't see the point to financially drain myself for nearly 10 years just to earn 30k and worry about the debt for most of my working life. On top of that some may want to become private practitioners to its not always the great picture of carrying out civil duties for everyone in society.NHS is not doing great at all and statistics simply backs that up.