Could be one of the reasons-
1. You don't know the doctor & have gone because of family pressure
2. You are doubtful of any treatment
3. You didn't like the way, the doctor examined you
4. The diagnosis is scary
If it's the 1st, 3rd & 4th, you can always take second opinion. In case of second, you can try home remedies, improve diet, be more positive & see in retrospect with more rationality if what doctor said makes sense.
All the best.