I don't think it's lack of common sense that's the issue. I think it's just ignorance plain and simple. Ignorance about whats going on in the world. Some people choose to make only the things that affect them on a daily basis the most important things in their life. As the old saying goes "They can't see past the end of their nose". Thus, they become indifferent to the things that they don't figure affect them or that they don't need to know.

Some people call this 'stupid'