Why do some universities not have a comprehensive exam? I spotted that some universities do not have a comprehensive exam for their PhD students while it is standard at most universities (specifically for computer science). For what reasons do some universities drop the requirement of comprehensive exam? What is the impression towards someone who has graduated from no-comprehensive department?
My department does not have a comprehensive exam. The most frequent reason I have heard is that we don't need it. On the other hand, some other departments in our university have comprehensive exams and I have heard that they are primarily used to weed out students after the first year.

I will venture to say that there is absolutely no impression towards graduating from a no-comprehensive program. Research job committees look at publications, letters of recommendation and research experience. Graduates from my program have found jobs wherever graduates from similar programs find jobs.