I know this section is marked as "not required", so we can submit the application without it, but it does raise some questions...
It may not be officially required, but it is generally expected and essential. I'm not an adcom member either, but I think submitting an application without a personal statement is a very bad idea.
Doesn't the personal statement only really count in our secondary applications? I'm not sure just how much schools put emphasis on this part of the application, when they already send you a prompt for the personal statement in your secondaries. Has anyone still received an interview invitation without a personal statement in their primary? I'm just not sure how much emphasis is placed on the primary application personal statement...
As I mentioned before, your personal statement is essential. It is your opportunity to show the side of yourself that isn't necessarily evident in other parts of your primary application. The personal statement is sort of like your personal calling card for medicine. The statement represents a slice of you; it is your best foot forward. You want them to call you back for an interview. The reader should leave thinking, "wow, that caught my attention; this guy intrigues me, and I want to invite this guy up for an interview." Be honest; show, not tell, the distinctive qualities and attributes that you wish to emphasize. Keep in mind what you are selling. Using evidence, demonstrate your suitability to become a physician and your motivation for medicine. This should be very personal, however; it should have the mark of your unique personality. Avoid trying to cater to your imagination of what adcom members like to see. They can smell that a mile away.
Your entire application is reviewed, including your personal statement. However, don't discount the secondary essays, either. They are also important. They are mostly an elaboration on your application. Many schools will ask some variant of "Why osteopathic medicine?" and "Why [particular school]?" and potentially other questions. They are looking for other ways to learn about you and trying to assess your movitation for, and knowledge of, osteopathic medicine, as well as your fit for their school. Medical school interviewers sometimes draw on your personal statement and secondary essays, in addition to other parts of your application, such as extracurricular activities and academic elements, to ask you questions during an interview. Thus, be honest, but compelling.
Take all of your essays seriously; get second opinions and make sure they are edited before submitting.