That's a question I've never thought to ask.
But as for keeping it all in equal sizes, I'd say if you enlarge the stripes, then enlarge the center square also. But on the other hand, as has been stated here often, it's YOUR quilt and you can do anything you want with it. And often you'll discover that it looks marvelous when you change things around.
It's like a recipe, add this and that, but if you add something different, it will take it from everyday foods to GOURMET!!
So go for it, and show us what happened when you did. We're all interested.