I think that last is a big part of why more chemistry professors don't push their students to look outside chemistry -- it doesn't help the professor or her future group members, either in the present or the future. If your graduate students and postdocs go on and perform good science, there is some amount of reflected glory to be had; it's not a coincidence that the introduction of seminar speakers starts with a ritual recitation of the speaker's former
If a chemistry professor was known for training people who left the field to be doctors, successful Wall Street analysts or high school teachers, would this professor win as much praise from their colleagues as one who had R1 professors and big pharma directors as their chemical progeny? I doubt it.
I should close this by noting that I like chemistry professors a lot and count my former research adviser as a friend. But they are rational actors, too -- and there is no shame in admitting that.