This is something I never understood. There must be hundreds if not thousands of applicants who have near 4.0 GPAs and 37+ MCAT scores. Sometimes, I swear this is the average premed at my medicine-obsessed university. Anyway, With so many applicants with high numbers, why are the average stats at even top schools usually so much lower.
I would actually bet that there are actually a fairly small number of applicants who get both of those numbers; it's far more common for someone to get an outstanding number in one of those areas (say 3.95 or 40) and then an average one in the other (say 3.6 or 32). Getting a near pristine GPA or top 2-4%MCAT are both incredibly long-odds results, so achieving just one of those is unusual; managing both is rare. Then, as someone else pointed out, there will be a subset of these who are disqualified for various other reasons: either they haven't shown that they can interact with patients (clinical experience), or they can't express why they want to go into the profession (bad PS), or they severely rubbed a key person the wrong way during undergrad (assassin LOR), or it turns out they're an arrogant prick (bad interview).
Furthermore, realize that those top schools DO probably still get a fairly large number of these applicants with "dream numbers." Say there's 100-200 out there. The catch is that they are ALL applying to the same top schools, and so they'll probably be spread out so that about 10 of them each go to about 10-20 various top-flight schools. That still leaves around 190 spots for other applicants.
Finally, in regards to the question of what makes the "perfect applicant," I'd say that at the end of the day there's really seven attributes that a med school cares about when examining an applicant: GPA, MCAT, clinical experience, research experience, strength of personal statement, strength of LORs, and (sadly) URM status. So the "perfect applicant" would have a 3.9+ GPA, 39+ MCAT, 3+ years clinical AND research experience, write passionately about medicine, get rave reviews, AND be Mexican.
My personal opinion is that, of the six attributes you can affect (not URM status, obv), you can be a strong applicant if you have average to above-average stats in five of those categories even if the sixth is a bit weak. There's really only a handful of "perfect applicants" out there, and you certainly don't need to be one to get in. I'd say if you can get 5 of those categories nailed, you should feel pretty good about your chances.