Why is using break considered bad practice?

I am currently in a beginning programming course at my University (I've got plenty of experience in the subject already, but I still have to pay for that piece of paper with time and money.) and the professor has been stressing since the beginning of the course that the break primitive that many languages provide is bad programming practice, and that many companies have policies stating that their programmers are not to use them.

He has yet, however, to explain why, and I honestly doubt he will.

As my earliest experience was with C, where I'd see switch statements and loops peppered with breaks, and I never thought anything of it.

So my question is "Why is it that break primitives are considered bad practice?" as stated at the top.