The fact it is so prevalent in the gene pool suggests there may be some benefit we are unaware of. Further study is needed.
No it doesn't. That's not how evolution works. It is not perfect, it does not march towards good, it rolls random die and sees if that leads to having kids or not. If you get old enough to have kids and have them procreate it very much stops caring.
Edit: and it doesn't 'cause', it puts you 'at risk for'.
And I said that the mutation causes massive increases in the rate of breast cancer. Which it does. Read more carefully if you're going to try to be pedantic.
Like go through IVF so that their children don't have to.