So I was told that the Kent's absolutely needed to be in Superman's adult life.

[exile001]

It's not that they were dead or alive in the original origin.It was that they were insiginficant..Weren't basic ingredients to make a superman.It was'nt suger,spice,earth parents ,skyparents and everything nice ...boom you got perfect(whatever that is) little boy.
The origin was kid fell from sky.Kid is super in an orphanage.gets parents(named only).Boom! smashes car and scares jackasses/bullies..It was like a minute detail in the original story.It was really the most uninteresting part of superman.The origin i mean.

I agree. That's understandable for a time when comic stories were 10 pages and intended to be disposable one-offs. It's not important to that origin which was only there to give context to the setting and powers.

But as comics have increasingly been about long form storytelling since the 60's (at least) they have more room to explore a supporting cast which is where I'm coming from. Comics now need more characters to remain interesting, flesh out a world and give main characters more people to interact with and show different sides to add depth. They see Clark, the boy they raised, and offer the reader that unique perspective on him as a character.

They don't need to be in every story. They could not appear for a year at a time (and have), but with them alive that option is still open to the writer should they choose to use it.