Just to add to what Lisa said, I think the difficulty stems from not having much data with which schools can evaluate you, rather than schools being biased against college seniors.

That being said, Lisa does a very good job quantifying the requirements for college seniors. Another elaboration, however: having a high GPA and high GMAT is important, in my opinion, not in that it will set you apart from the rest of the field. Rather, a lot of schools want young applicants who

1) can bring some added insight specifically into classroom interactions, since they are fresh from school (and having a high GPA/high GMAT may be a good indication that you are a serious participant in class)

2) would have been a good candidate for b-school later on, but because of their stellar profile and reluctance to wait may choose to go to law/med school now, and forgo b-school as a graduate school choice (again, those who would be considering the top law/med schools generally have very high academic scores)

Hope this helps!