We have socially conditioned ourselves to ignore signage if we aren’t specifically looking for it. 99% of signage in today’s world is usually just an ad being shoved into your face trying to sell something. It is a bombardment of annoying and intrusive information to the point our minds have trained themselves to filter the visual noise out. It is literally too much for our mind to process, so most of it gets deleted from our consciousness in the same way the hole in your vision from your optical nerve is being hidden from your perception unless you specifically expose it.