You're right; there must be students with no work experience that get directly admitted into a top b-school, but understand that that is an exception to the rule. Generally speaking, person without work experience is not gaining admission to top b-school. One thing you have to think about is when companies recruit on campus, they'll inevitably ask "what did you do before business school?" Everyone will have a good answer to that, whether it be brand management, marketing, consulting, banking, clean-tech, whatever, and you'll stand there and talk about internships. It simply won't cut it. You need to have a good reason to tell the recruiters why you're better than the next person who came from a good school, with good grades and work experience. This same mentality translates to business school admissions process. Without a logical explanation, b-school admissions won't take a chance to admitting you when the next person has everything you have, but with real work experience.
GMAT Club Premium Membership - big benefits and savings