Why don't men get breast cancer?

They do. Male breast cancer exists, but is only 1% of breast ca. Females develop breast tissue in response to hormones at levels that men don't achieve. If men take certain hormone medications, their breast tissue can grow. Breast cancer cells can be estrogen sensitive, so genetic males taking estrogen or with liver dz may be at increased risk. Brca gene can also increase risk, as in females.
They do. Men do get breast cancer, but their risk is considerably less than the risk in women. Breast cancer is a disease of hormonally-active breast tissue; therefore, with very little breast tissue, their risks are much less.