"I wonder how many other things our monke brains completely ignore"

The typical visual examples are having unified binocular vision from two seperate sensory inputs, and filtering out eye movement and blinking. When i got my last pair of glasses, they had very notable reflections on the edges of my field of vision, which completely disappeared after two days, and by disappeared i mean they are still there and my brain has just learned to filter them out. Just as i usually don't notice the frame at all, or how they edges of my visual field, the parts not covered by my glasses, are blurry as hell.

In theory, you can feel the position of every hair on your body, you've got the sensory apparatus for that, and that's probably hundreds of thousands of individual hairs, yet you only notice them in very specific instances. The amount of ambient sensory input that we are submerged in all the time is staggering. Most of what we perceive of the world is pushed aside before it becomes conscious and takes up our attention, we are constantly observing only a tiny, subtractive sliver of reality. As anybody who has ever taken a large dose of LSD can attest to, this is kinda useful, as navigating your environment is sketchy when you are unsure of where your proprioception ends and tactile sensation of the outside world begins and you feel like turning into a human-chair-hybrid every time you sit down.