I just don't accept that the death of a parent is somehow an obligatory part of every fictional character's backstory. That's too formulaic. Superman got by in comics and TV just fine for over 20 years with both adoptive parents alive -- obviously it is possible to tell good Superman stories without orphaning him a second time. It. Is. Not. Required.
You're right that it doesn't need to be a part of every
hero's origin...and I am not
saying he needs to bean orphan.
But having Superman not
able to save a "weaker" human who has protected him his whole life, and who has an especially strong hold on his heart (his 3rd weakness) -- that's powerful.
Also, knowing that a big part of his life is gone..again, makes the "god" a real human.
Other Superheroes can have their parents intact....but losing just one (and it could
be Martha; mothers rarely die, and even rarer, a widower survives), would be enough for Superman.