There's a lot of science in medicine. It is often called the youngest science, and rightly so. However, the practice of medicine is quite different from most sciences because it is so intimately tied with dealing with people. And one of the problems with dealing with people is that despite whatever evidence you may have, people need to be convinced.
One of the tremendously annoying things I discovered in med school was immunization of children. So many parents had so many bizarre (and frankly ludicrous) reasons not to immunize their children. After a while, it just wasn't worth fighting over. Now, it's not uncommon to see outbreaks of mumps and measles. Measles is a disease I can't even recognize. I've never seen it.
But immunization is only the tip of the iceberg. I fought over the phone and in person with a patient over the course of a day to agree to have a cardiac catheterization. Once in the lab, they saw left main and triple vessel disease.
One of the things I love about adult medicine is simply that: it's adults. If someone wants to make a tragically bad decision, at the end of the day, if they were properly informed, it's their terrible decision to make, and I can sleep easy at night.