Right. You don't get people switching to Biology because it is too hard, what you do get is a ton of Biology students that have no real interest in Biology and just want to "become a doctor" (note that they do not really want to practice medicine).
Actually, (even with no evidence) I believe that at least a third of these people have no real interest in biomedical research, they are just doing it as a graduate student because there are almost no other options available. They did not make it into Medical school (or could not afford it) and have no other option with an undergraduate degree in Biology.
Not going to medical school and with no real idea of what to do in the 'real world' with their biology degree and an advisor talking about grant money, they are encouraged to apply to graduate work in biomedical research or something similar. They don't really care about it though, they are just failed doctoral students.
Call me biased, but too many freshman level advisors tell people to study Biology.