I take it to mean professional interests, too. The medical profession needs to admit some people who seem like they may be more geared towards primary care, some who seem like they're headed for psych, some who will probably gravitate towards radiation oncology, or ob, or what have you. Even broader than that, for the future of medicine they need to find people with public health interests, people who plan to research, people who enjoy business and may become hospital ceos, etc, etc.
Regardless of how well they did on the mcat, if US med schools start accepting only, say, physics majors, or biochem majors, or philosophy majors, before long medicine in this country would be very different.
Clearly this isn't a perfect correlation - a lot changes in med school. But I'd bet physics, biochem majors are much less likely to enter psych and fp, psych and poli sci majors are much less likely to gravitate towards radiology.
There are a lot of different kinds of doctors out there, not just in specialty, but in personality, focus, interests, etc, and they all play a role. Everyone has their place.
This is important to keep in mind...Because no matter what group you fall under, before long in med school you'll be wondering about some people, how on earth did this hippy communist/stuck up science geek/elitist tool/raging feminist/whatever-else-you-can-think-of get into school?? Do we really need doctors like this?
Remind yourself, yes, we do.