There was an article in psychological science this month investigating the reasons that when public and organizational policies have a default (such as organ donation defaulting to opt-out), people generally stick to the default. The research concluded that people assume that the default is a recommendation from the policy makers of the best course of action.
I wonder if there is a correlate in usability. Does the typical user, who notoriously leaves settings such as virus protection, operating system defaults, etc. at the default, also have this unconscious assumption that the software maker recommends the defaults? That would be a much different conclusion than it is simply laziness.