'Benefit' is a loaded term. It involves contestable points like whether goodness is subjective or innate and whether a person's awareness of the benefits of a behavior is necessary to make it truly beneficial (which can be true or false regardless of whether goodness is subjective or innate).
Different personalities exercise varying degrees of honesty in different situations for different reasons. Some will end up being truthful more often than others. Pretty much the only way to "not lie" is to train yourself to be open minded and to recite information as plainly and objectively as possible.
Generally speaking, people will "lie" without being aware of it simply because it is more entertaining.