[fao_]

Because cultures and their beliefs can be stupid, and religious/cultural dogma can perpetrate a system that doesn't work. Humans tend towards efficiency only where there is no ideological dogma to hinder this.

Take the example of sacrifice. In dozens of cultures spanning ((in some cases) hundreds of) thousands of years, people have believed that the sacrifice of <insert species here> will stop the rain/volcano/thunder & lightning/etc. we now know this to be completely false, even though many of these cultures have writings and other 'empirical evidence' that says it does work.