It's also the mindset, and the surrounding area of where URM's live. Also the fact that most URM's don't have white collar workers in their families, thus, they believe that being a "Physician" isn't for them. So it's not about hard work, because many, many minorities do hard work in other areas. Who said that hard work entails studying from a book? Or going to lectures? I know many classmates of mine who say that they won't become a physician because that's for "smart people".
Yet, those are the same individuals who weren't pushed in high school. They weren't screamed at for getting below a B. I knew an Indian kid who was in 9th grade, and whenever he got below a B, he'd be so pissed. I used to ask him why he used to get so upset, and his reply was that "His father would hit him if he got a low grade"
And this was the case with many Indian kids that I know.
Most parents that are hispanic just tell their kids to graduate from high school, which was the case in my family. However, my father being a white collar worker, and him pushing me to go to college and be successful, was the push I needed to consider medicine as a career. A good majority of people who apply to medical school have white collar workers in their family, or perhaps other physicians.
So FYI, making that assumption about URM's working hard is a moot point, because I know many latino parents who work around the clock, who don't see their children basically at all, and they most likely aren't even hitting the 50K mark. It's not about HOW you work, it's the principle.