Some people love to run. They enjoy the process of working up a sweat, spending time in their own head and feeling their body work at its peak. These are the people that often experience a runner's high. They are focused, motivated, and perhaps are just built in such a way that exercise is pleasurable (for the record, I am not one of these people). If they pull or sprain something, they see it as an overcomeable obstacle, just an occasional part of the process. When they finish they still have energy despite the physical exertion, and are proud of their efforts.
Others don't like running and avoid it completely. It may seem too hard or too complicated to fit into their life and the rewards seem abstract or unattainable. There are others who don't intrinsically like running but do it as a means to an end. They know running can mean the extra cost of good shoes, occasional sore muscles and perhaps the loss of sleep, but those loses are balanced by the benefits. Some days they wake up ready to hit the pavement and other mornings the snooze button seems mighty tempting. Either way, the joy is not usually in the actual experience but they do it anyway.
Birth is no different. Some people will look forward to the experience and enjoy the full process of giving birth. Some women, be it due to preparation or their own unique makeup, will not feel pain during labor and some even claim to have orgasmic births (for the record, I am also not one of these people). Other women will make choices to avoid the experience of labor completely. However, most will fall somewhere between these two extremes.
Like running, birth takes effort. In our culture, choosing to birth naturally may bring even more effort. There may be extra costs (often for midwifery care), the extra time needed to research evidenced based practices and then securing a provider that uses them. There are also the possible discomforts of late pregnancy (no routine, but generally unnecessary, induction by 40weeks ), and holding firm to choices that may put you at odds with your care provider (not scheduling the aforementioned induction) and of course labor can sometimes be, well, uncomfortable.
There are lots of reasons moms choose natural birth. Some are motivated by the health benefits conferred to mom and baby during the natural birth process. Many are motivated by the love of birth and the belief that their body was wonderfully and fearfully made for this feminine task. Some are just motivated by the possible negative consequences of a managed birth. Like the runner though, each pregnant women (in this country anyway) must decide if she wants to figuratively lace up her jogging shoes and how she will run the race.