I think this is why it's helpful to think of it, not as a 'why', but as a 'how'. There are tons of things about our bodies that do not make sense, but which hasn't killed us enough to not spread. These can still have an effect on us, and that's what's interesting to me.

Trying to get a reason out of evolution can be useful sometimes, when we actually want to know what lead to a trait becoming common, but for most things, especially concerning humans, the 'how' is so much more interesting, because we can actually get concrete answers to that.