I found the scyscraper or tower analogy to be very good for describing the issue. If your 7th floor is built with cardboard you can't "just add" an 8th floor on

I found the scyscraper or tower analogy to be very good for describing the issue. If your 7th floor is built with cardboard you can't "just add" an 8th floor on top of it and you can't quickly hack the integral structure of something on floor 2 because if you do you eventually end up with a game of jenga.