Most people don't see half of what's in front of them. Your visual cortex does a shit load of imaging processing before the signal even gets to your brain, whose priorities are still checking the ancestral Savannah for dangerous predators, edible berries and climable trees. That's why a sudden cat in the night can make you jump and some people when distracted, can walk right out in front of a bus. Your brain just isn't interested in those large moving chunks of metal or the static heaps of brightly colored stuff that piles up in drifts around us. Never mind all that, says your brain, it's those silent fur-covered merchants of death you've got to watch out for.