I agree with it being a vital part of Smallville and Superman I & II. But I don't agree with it being vital to Superman. Sure, there's plenty of stories where the father seems to have to die before the son can venture off to do great things. It's a story that I, personally, can relate to. But for God's sake man, Superman lost an entire planet (or country if you want to strip things down). In my mind Superman is all about preventing the destruction of another world...
Yeah, the point of losing Pa is not about him preventing a planet's destruction or even about the father having to die before the son can accomplish something.
It's meant to be the point where Clark learns that he can't save everyone and he isn't infallible. It's about why he has humility despite his godlike powers.
That's why pre-Byrne (who, god knows, is far from able to understand a character with humility), the death of one or both of his parents was always part of the Superman origin. It was the failure before the triumph.
