@Almighty Saguaro
I understand your frustration about this. I believe a few studies have shown that the earlier you apply in the med school admissions process, then the better your chances are overall at gaining admission. To me this doesn't just mean that your AMCAS should be submitted as early as possible, but also your secondaries, letters, transcripts, MCAT scores, etc for precisely the reason you said - securing an interview early in the admissions cycle. It is a little misleading I agree, since many schools don't have secondary deadlines until November, or even as late as January. Unfortunately it is unrealistic for schools to hold off on reviewing applications until every applicant has submitted all materials, as that would mean they could not review applications/begin offering interviews until at least November (or later, depending on the school's secondary deadline). The way the application process is now: AMCAS opens in May, AMCAS submission in June, Secondaries sent out July-Septemberish, Interview Invites go out August-Novemberish, and Interviews September-February, Admissions Decisions sometime in March, and applicants committing to a school by May 1st already takes a full year... so lengthening that process even more would not be well-received. Alternatively, schools could change their secondary deadlines to be earlier, such as September 1st or October 1st, which would alleviate some of this perhaps.
And as
@heebeejeebies said, many schools don't make any admissions decisions until they have completed interviewing all candidates
Take home message: get your secondaries done as early as possible to put yourself in the best position possible to receive those interviews, and ultimately, acceptances.
Bonus: The good news is, it's only August. It's still very early in the admissions process - I don't think you're at much of a disadvantage at this point (you may have missed out on the first "wave" of interviews at a few schools, but there will be quite a few more to come)
Hang in there, and good luck.
🙂