What was the need for? Raman and Shagun?

I really don't watch this serial regularly or for a matter any serial until something interesting comes up but I do keep updates on it.

After seven year leap the leads life are in mess they had created for themselves.

But what I could not understand is what is the need for Shagun and Raman to act as married couple for Pihu's sake.

They could raise the child giving mother and father's love even without showing as married couple.

I really could not understand their point of view. One day Pihu will come to know the truth even if they try to marry now. What will happen then? Another Adi or Ruhi who will try to make Raman and Ishitha never come together or trying to bring them together.

What is CV's really trying to show?