Yes, but also, in last year's series, they made a point of showing how Rose caused all sorts of problems by preventing her dad from dying when they went back in time to the moment of his death. Having altered the course of time, events started getting jumbled up and these screeching monsters appeared and caused havoc, that the Doctor said were like bacteria rushing to a "wound" in time. Only by having the dad sacrifice himself was the wound healed and everything reverted to normal. So I reckon that storyline was included partly to demonstrate that he can't just time-jump back to prevent the bad stuff. (As well the guys above saying it'd just be boring and lazy!)