Darth Venal said:
C3PX:
Since Luke's father and Darth Vader were two different people when the first SW was made, Luke growing up with the Skywalker sirname didn't matter. Had George thought of the whole hiding Luke from his evil father thing while he wrote the first film, I am sure he would have seen fit to change his sirname

Actually, that wouldn't have made any difference. Why? Because he didn't have to give Anakin the same surname. Luke Skywalker could have been the changed name, but he instead chose to keep Skywalker as his father's surname.

I don't really see why it had to be changed anyway, because Vader was never going to return to Tatooine and wouldn't have known he had a son to go looking for.

I was reading the novel for A New Hope (which was written in 1976) and Vader says that Tatooine is a 'miserable planet' - now we know why he would say this.