The problem being that over generations, memories get garbled, traditions become either based on what is no longer assumed to be true, or altered to suit those in power. This happens in the short term as well, as we quickly develop habits and then continue as we've "always done it this way", or adapt to fit a new directive, without much consideration as to why our habit or pattern began.

Humans are good at patterns, but horrible at time. This is possibly because our perception of time is at odds with how "reality" actually works, but that's a far more expansive topic.