Fair enough, it meant a lot to me that Clark went to Metropolis to meet his destiny after the death of his aged adoptive parents...that was a real connection between the ages for me, more meaningful than making them young again or living to his adulthood...but we all have our symbols, I guess...
In the initial years of Superman, there was scarcely a difference between "found by a passing motorist and raised in an orphanage" and "found and raised by parents who live just long enough to send him onto his first real story". It was just background filler to get to Superman as a man. Their first names weren't consistently defined for the longest time.
As his Smallville past started became more developed, when Ma and Pa Kent became more than deathbed speeches, it made less and less sense to just jettison them as background filler. That's especially true since Superman already has a set of dead parents coming out the gate.
Look at the Superman I movie. Even with Pa Kent dead (and Ma Kent doing a silent Aunt May imitiation), he's still talking to Superman. Why lose that? The only reason he had to be dead was so he could be a booming voice in the heavens along with Marlon.
Does Superman need Pa Kent to be dead to do death to tell him he's not a boy anymore, to send him off into the world? With a fleshed out past, one in which Clark is raised to greatness, I just don't think that's the case. As far as I can tell, anout the only purpose for their death would serve was to show that even a Superman isn't a god. But that got so convoluted during pre-Crisis with alien space plagues and de-aging and whatnot where it just never really resonated with me.