The majority of CS students (including MIT) never studied CS before coming to college. Unless you propose MIT/CMU/Stanford/Berkeley/etc. only admit people to their intro CS classes who have studied CS before (chicken and egg problem, anyone?).
Well, MIT's intro calculus classes are overwhelmingly for people who have studied calculus before. Making it an actual requirement wouldn't change much.
As of 1979, the 18.01 I took matched what I understand is the the AP Calculus BC sequence, and while having previous exposure to the calculus certainly helped, it wasn't assumed.
