One day our professor was discussing
a particularly complicated concept.  A
pre-med student rudely interrupted to
ask, "Why do we have to learn this stuff?"
"To save lives." the professor responded
quickly and continued the lecture.
  A few minutes later, the same student
spoke up again. "So how does physics
save lives?" he persisted.
  "It keeps the ignoramuses out of
medical school," replied the professor.