The answer to "why?" is really just "Evolution". It's not satisfying at all, but for example sleep could have been an evolutionary accident that happened to hav

The answer to "why?" is really just "Evolution". It's not satisfying at all, but for example sleep could have been an evolutionary accident that happened to have enough upsides and little enough downsides that it persisted. As such, it could really be like the article described that it's kinda of a mis-feature of some other neurological mechanism, and the downsides weren't big enough to be selected against. There may also be an upside, I recently came across a study that claimed that participants that had a song stuck in their head for a longer time were more likely to hit the correct pitch when singing it. Not sure how that would translate to selective advantage though, if at all...