This concept can be scaled up to a lot of things, like why most of our systems break down. Nature only maintains what is needed to continue the species, everything that happens to you afterwards, with the exception of child-rearing, will be abandoned by nature unless someone gains some trait from living longer that helps the species propagate.
But nature is kind of silly, it doesn't make "choices" so some of the adaptations can be weird. Like how our retina's blood supply formed on the front of the retina so your brain has to always edit out your blood vessels from your vision and you can only see it using special tricks of light and then BAM all the spaghetti appears that's been there all along.
Imagine what else our brain tells us and shows or doesn't show us to make sense of what evolution has turned us into.
The idea is that if you can make your surroundings as dark as possible, then shine a very small point of light into your eye and wiggle it so there's a shadow changing angles rapidly across your retina, this will make the blood vessels you can't normally see shift slightly in your field of vision so your brain forgets how to edit them out and they pop into view.
Yep! Or even how you usually breath without thinking about it but can take over manual control. Your brain does a LOT of things with your senses all the time that you don't notice, it has layers and layers of intelligence that makes decisions on what it will "report" upwards, so you depend on basically a vast system of managers or sub-officers that are conscious but have no language, to fully captain and control your meat-ship.