Why do some spiritual people believe when a person suffers from a disease or a cancer, they have been cursed?

I actually don't think religious people think that way, the ones that do are biased. Things happen in our lives whether we like it or not it is truly hard to explain. I feel that people that go through these different physical obstacles stronger in the end. I have had my physical issues as well which sucks but I have been able to deal with it to.