Imagine a reader who is not one of your lucky “most” majority. Imagine a reader whose cancer was not caused by the bad lifestyle decisions that you listed. Put yourself in the position of somebody who undergoes extensive surgery/radiation/chemotherapy and then lives with the side effects of these treatments. Consider what it’s like to live with the fear of recurrence even after such treatment. Then maybe you’ll understand why people might be excited about the potential of this sort of screening.