A lot of people will lie all the time. Usually for emotional reasons. (insecurity, fear, etc). Most people don't lie specifically to manipulate, but rather to protect themselves from a more uncomfortable situation.

This also happens with personality-disordered people (particularly, Narcissists, and especially the Borderline PD people I know . . . they SEEM manipulative, and they technically are, but they're manipulating for a reason that's usually ego-defensive).

Psychopaths, on the other hand, will lie for no damn reason at all that makes any sense to a sane person.