I don't really see gravel paths, dirt roads or even some mild trails as a reason not to have drop bars on a bike. Most cyclocross racers use drop bars and there have been a few drop bar MTBs over the years. Most notably the early Bridgestone MB-1 and the bikes Jacquie Phelan won MTB championships on in the 80s.
Not to say that drop bars are the best choice for riding on rough terrain, but that it can be done safely and effectively. I've done some tight singletrack on the 3rd bike below and it wasn't that bad.
