I think you're actually incorrect in inferring that "many people prefer undergraduate medicine course(s)". Who says so? I think there's room for both methods of entry, as both have positive and negatives alike. Limiting the method of entry essentially limits the kind of candidate accepted into medical courses. By opening up to graduates, the intake becomes diversified, and picks up students who may not have considered medicine in high school.
Additionally, the different curricula attracts different types of learners. For instance, grad entry courses may provide appeal to students who prefer early clinical contact or self directed learning, and undergrad courses may attract gifted, dedicated school leavers. Personally, I don't think I would have enjoyed the structure of the undergrad entry courses that were in operation when I was a school leaver, to the point that it would have been enough to dissuade me from applying at all (had I hypothetically have wanted to apply in the first place). As a graduate, the grad entry courses held far more appeal - enough to hold my interest long enough to investigate further and apply.
There's definitely room for both 
) is that there is much less room to explore other interests within an undergraduate course. Your classes will be largely dictated to you, as will be your timetable. Many people have interests outside of medicine which use other parts of the brain. I had 3 general courses, they were incredibly refreshing.
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