I'd just like to weigh in on this subject as a current MPH epidemiology student who is applying to medical programs:
First of all, I've decided to pursue both an MPH and MD precisely because my professional ambitions are tied to both public health and clinical medicine. My specific interests (beyond clinical medicine) are in healthcare-associated epidemiology, including antimicrobial resistance, healthcare-associated infections, and how to improve the safety, value, and quality of healthcare from an epidemiologic standpoint. As you can probably imagine, jobs in these fields require background in clinical medicine in addition to public health. For the issue of jobs requiring both an MD and MPH, a cursory glance through job postings by local, state, and federal public health organizations will reveal such jobs as chief medical officers, lead researchers, and international branch leaders that require an MD as well as basic public health knowledge and experience. Obviously if your career aspirations don't align with this type of work then an MPH will be of more limited value professionally.
As to why I've decided to pursue an MPH before med school, I had the opportunity to attend one of the top MPH programs in the country without accruing any significant debt and I felt that I wouldn't get nearly as much out of a one-year condensed program vs. a full two-year program. I've had opportunities to develop professional networks, conduct original research, and work with organizations that I wouldn't have had were I to have decided to apply to med school directly after undergrad. Sure it's a nice boost to my GPA, as the program is geared more towards establishing professional connections and fostering professional development than towards academic rigor, but that's certainly not the primary motivation for seeking the degree (although I recognize that this may not be the case for students who are using the MPH as a stepping stone into med school). That said, it's worth thinking about what you want to do with your medical degree and whether or not an MPH will be a professional asset, but in most cases there's probably not a rush to get the MPH. Much like every other degree out there, what you get from the program is correlated to the amount of effort you put in.
Regardless of your reasons for pursuing an MPH or what you think of public health, it's certainly more than creating checklists and arguing over research findings. It is worth noting that even if you go to medical school and become a physician who never steps foot out of the clinic or hospital ward, you will still have professional encounters with local, state, and federal public health agencies. The individuals at these organizations are your professional colleagues and are often more knowledgable about diseases in their expertise than many practicing physicians.
