For some reason, this sparkle, this feeling vanishes in many people. They become happy cogs of a big working machine called society. It seem to me like a life full of despair - they are just waiting for death to do its part. No ambition, no nothing - barely staying alive, at the expense of others if required.
Some say it's the children effect. I've had friends with children explaining me seriously that they would do everything for their children - and when I tried to explore that (I really wondered about this "everything") they said up to killing innocent people for the sake of their own children.
Some quote philosophers saying that you either create children or you create yourself. There might be some truth in that, but I don't believe it is the whole thing.
This sparkle persist in some people, with or without children - not just founders, but from all the parts of society. That is what IMHO makes humanity move forward.
Regardless of one political opinions, this is something also very deep in Ayn Rand work - refusing mediocrity, living for the sake of it, to achieve big things, the things one loves and dreams about. I don't know many authors where this is so beautifully said.
"Real life" may be about renonciations, but if having children didn't do it, too many renonciation might kill up the sparkle for good.
Preserve it, cherish it - it's the most important thing in your life.
EDIT: downvoted already. I see HN is just as liberal as often, and saying "Ayn Rand" regardless of the context is worthy of a negative vote. Whatever.