hmm, as I see it, it is explained through the individual social construction of the world. So the early socialization builds up the foundation. As you told us your parents were quite conform with telling lies. This would lead likely to a perception of the world that telling lies aint bad. Gladely you can change this worlds :) So the question which remains is: " Where the parents got this ideology?" From there parents? Media? Society? Probably a mixture of all of them. Fact is that lying is quite accepted in almost every cultural landscape, but still, why we lie is not totally answered with that.