It's, well, just the way things work where I'm from. Cosmological propagation. The parent dies as it births the child.

[ It's a basic concept on Kanaya's planet, where families just don't exist, trolls only hatching from parents who've been dead hundreds of years. Or how Kanaya had to cut Ashiah's egg from the corpse of her mother. Legacy always came with sacrifice on Alternia. ]

Though, I guess it helps to understand it when you've seen a universe from the outside. When you can perceive them as living beings, rather than abstract concepts of Space.