Everybody here is approaching the idea of these prereqs from the perspective of a practicing physician. Yes, in that case, ochem might not be the most useful thing in the world.
However, keep in mind that the world of medicine also depends on research. MDs do research too, along with the MD/PhDs. In that situation, having an understanding of science at a fundamental level is important to be able to keep up with new developments.
Yes, pchem and fluid mechanics and such are important at a fundamental level, too. However, they are more advanced and would be impractical for someone with, say, a biology major. Organic chemistry is actually an introductory level class at most universities.