I had two papers published during my undergraduate years because my writing was head and shoulders above every other student in my department. Granted, I also put more work into my research than anyone else, but the deciding factor that made the head of the department eager to publish undergraduate research was the clarity of my writing. Needless to say, when it came time to apply to graduate school, having two papers published as an undergraduate was one hell of a plus.
At the graduate level, thankfully, the story is a little bit different. The SATs did not always have an essay section, but the GREs have had them for as long as I can remember. Multiple choice tests, even as sophisticated as the GREs and SATs are, do not give an indication of a student's ability to organize their OWN original thoughts. It always struck me odd that the SATs did not include any sort of writing when I took them.
In any case, the quality of students at the undergraduate level is really to blame here. By the time you get to graduate school, academia filters out most of the dumbasses (except in the case of basket weaving and MBA programs).