And I know plenty of people from my class who were fully aware of pathology (even were members of path interest group) but went into dermatology and even physical medicine & rehabilitation because of better job prospects. You need to be aware of the specialty to choose it, but in-depth exposure is not necessary. In fact, exposure to too much pathology (autopsy, heavy grossing) is more likely to repel a lot of good applicants.
And to say that most American medical graduates are not aware of pathology and the role of biopsy, at least to diagnose cancer, is utter nonsense. On my first IM rotation, I was asked three times to call pathology to get TAT on biopsy results by my attending. Even during the second year of medical school, when we practiced presenting patients, my classmates and I had to check pathology results for that abdominal or lung mass, and it wasn't a mystery to anyone what biopsy was and who interpreted it.
While there is no direct evidence to say that exposure or lack thereof plays a key role in career choice, based on the data from other fields with minimal to no exposure in medical school curricula but high proportion of American medical graduates (e.g. radiology, otolaryngology, child neurology, anesthesiology, neurological surgery, orthopedic surgery, vascular surgery, physical medicine and rehabilitation, dermatology, plastic surgery), I conclude that depth of exposure in medical school is probably not a significant factor. Ironically, fields with most exposure (e.g. family medicine, internal medicine) but lower prestige/crappy lifestyle tend to have lower proportion of American medical graduates.
Lack of exposure to pathology in medical school curricula serves as a scapegoat for pathology leadership who gladly sweep under the rag the real problems our field, one of the most interesting and intellectually stimulating fields in medicine, is facing.