Why should women have mammogram?

Answer 1

There are two big issues:

1. It's fairly common for people to have the general belief that if they don't know there's a problem, there isn't a problem; this make people reluctant to have medical tests in general.
2. Mammograms are physically at least somewhat painful, particularly on older equipment; to get a good picture, the breast is compressed in what amounts to a vertical vise.

Answer 2

To detect any breast lumps and if the lumps are cancerous, to catch the cancer early, as it might be harder/impossible to treat later.

Answer 3

Below age 40, breasts tend to be "radiographically dense," which means it is difficult to see many details.