Since Computer Science pervades many fields these days, it make sense to have a CS Minor. Unfortunately, aside from J. Gutag's course on computational thinking, not much time seems to be focused on the how's of computing and not much on the why's and what's.
Why are course 7 majors not allowed to do this? Weird.
Looks like the same reason as 18C: because if you want to do CS and biology, you should major in computational biology, which is course 6-7. (I had to look up what this new-fangled 6-7 is.)
(sorry about all the numbers, non-MIT folks, it really is the way we talk about MIT majors)