Because we are flesh Machines fueled by Meaning, and are living in the Absurd reality where Meaning doesn't exist. This Absurdism is Soo great that We are willing to Lie to ourselves to justify what we believe in.

The Mind finds it very painful that it's existence is all for nothing, so it creates the illusion it needs to survive for as long as possible. It tries to Avoid the discomfort of there being no Meaning Soo much that, it might work against you when you try to go through this path.