Double Mastectomies

I sometimes wonder about the choices that some women make to have double mastectomies (have their breasts cut off) because they may be at risk of getting breast cancer. Ie it may be in the family, they may carry the identified gene.
All I would ask is if there was a history of brain cancer in the family would they cut off their heads?
If there was a family history of heart disease would the cut out their hearts? It just sounds stupid doesn’t it?