Because 99% reality, 99% of all-there-is is invisible to most of us, we all developed some way to cope with that… and of those the most damaging, the most harmful is assumptions.
You assume you know. Youe assume the context. You assume what is wanted and needed.
The only effective method to make something work is to remove, little by little, all the things that make it not work, or not work as well as it could.