The useful answer is rarely, "because they're stupid." Or even, "because they're evil." In fact, most of the time, people with similar information, similar beliefs and similar apparent choices will choose similar actions. So if you want to know why someone does what they do, start with what they know, what they believe and where they came from.
Dismissing actions we don't admire merely because we don't care enough to have empathy is rarely going to help us make the change we seek. It doesn't help us understand, and it creates a gulf that drives us apart.Empathy doesn't involve feeling sorry for someone. It is our honest answer to the question, "why did they do what they did?"
Cannot stress about how important it is to ask these questions when you are doing your user research. I have always asked random, unrelated questions that has paid of in the end because it allows me to know where the user is coming form. What type of gadgets they use and what type of apps and software they use in their daily lives has an impact on how they are using a particular system.
Its called "User Centered Analysis" for a reason.