Because empathy requires effort and a certain level of intellect. My personal experience is that less educated people tend to view the world through a filter of their own experiences and don't realise (or choose to ignore) the possibility of a situation vastly different to their own. Highly educated people are exposed to philosophies and opinions that provoke thought and analysis. They are used to engaging in thought experiments and utilising imagination to consider many facets of an issue. I suppose you could say that they are trained to think rather than view something at face value.