In my mind, the difference between science and engineering is that science is concerned about what's provably true, whereas engineering (and I include applied math and even medicine here) is about getting to a result.

Therefore, our medicine is not perfectly safe, our cars are not perfectly safe, our building are not perfectly safe, we don't / can't provide 100% health coverage to everyone, and so on... but in aggregate, they make the world a better place, so it's worth it.