Q. Why should I have to study physics if I'm going to be a doctor - lawyer - etc?

Short answer: Physics is cool, but I'm biased.

Longer answer: Physics, as a discipline - especially at an undergraduate level, teaches many things that are important in all walks of life:

1) Problem Solving skills - the typical physics course is more problem solving based than any other subject (except perhaps mathematics) and the problems are often more practical. If you want to be a doctor, say, skill at quickly thinking about the problems of "what is wrong with this patient" could mean the difference between life and death.

2) Real World Familiarity - Freshman physics courses tend to teach about the every-day, real, world. You learn about how things move, how they fall, what friction means, what constraints conservation of energy and momentum can put on a system.
Imagine you're now a lawyer, defending an innocent man accused of a murder. What if the prosecution's theory of the crime had a small, but telling flaw in the physics - a problem with the trajectory of a bullet say - pointing this out convincingly would make your case trivial. Of course you would get an expert witness in to testify, but how would you know there was a potential hole there if you hadn't honed your physics intuition? And how will you interpret the physicist's testimony for the jurours if you dont understand any of it?

3) Relevant information - Physics is directly relevant to the core of many fields which might seem seperate at first glance. Engineers build bridges, but they need to understand the forces involved and how bridges react to stress in order to build safe ones. Biologists look at proteins and DNA - the structures of which are measured using diffraction techniques developed by physicists, and only really understood through physics. Biologists also use light and lasers to make flourescence measurements to keep track of the chemicals present - physics illuminates (if you'll pardon the pun) the devices, lenses, microscopes and the very colors of the dies used!

As you can see, there are many good reasons to study physics, no matter what your career goal might be - but the most important is that physics is constantly unveiling new facts about our universe - from the very small, like new semiconductors and superconductors, to the very large, like black holes and galaxies - do you want to understand what is coming, or do you want to be left behind?