That is because science is continually improving. There is a possible cure for cancer now, and most diseases can be cured or controlled by modern medicine. It has also been proven that the mind can cause the body to do wierd things when it really believes something. For example, studies have been made where people who received a sugar pill did as well as people who received the actual medicine when both groups had been told that they had received that medicine. It is the same with faith. People believe that faith helps a lot, so, just like the sugar pill, their mind tricks their body into believing that it does.