Have you ever tried to rekindle a friendship with an ex?

I'm just curious.
I know many will say that it's a waste of time but I do wonder why we are often so cut throat.
If substantial time has passed and you are decent people accepting the boundaries making it a platonic relationship.
Why can't you be friends?

I often feel that a person that's been that intimate with you, will now be past all the "giggles and awkwardness" and just see you. Especially if their intentions are good.