Because businesses, along with society in general (especially US society), is very bad at making evidence-based decisions. That extends to changing policies and procedures according to evidence of what works well and what doesn't. In fact, in some places (the US again comes to mind, which is where I live) it goes in the opposite direction of effective and evidence-based. I think it's because of psychopaths - which I define as someone living in a fantasy world who wants to control and hurt others.