But what if, you have 1,000 Bitcoins in your wallet, and you forget one word, JUST ONE WORD, and you have no copies of your seed phrase anywhere because "remembering 12 word is not that hard". You'll definitely know the true meaning of manual brute-forcing. Hahaha.
One missing word from the seed is not too much of a problem, I think that finding even three words is feasible with today's technology in some reasonable time. As time goes on computers will become more and more powerful and some who have really messed up with their backup hope to be able to discover their treasure chest.
Of course, a lot of bad things can be avoided if we take some basic precautions, and one of the basic ones is to understand that only one backup represents a big risk, but even 2 or 3 in the same location in some cases will not help if it is about ordinary paper.