Poor planning is too frequently blamed when things go terribly wrong. What if there had been no concept of a plan and things still went wrong? What if there was a "good" plan and things still went wrong? Random outcomes will always outnumber the considerations of the most sophisticated plan.
Architects and engineers are tasked with describing the outcome of a design within the limits of the rules of geometry. If a room needs to be a minimum of ten feet wide, then the architect would do well to make it twelve feet wide. What if the client doesn't like the room? What if the client buys a sofa that is fourteen feet wide? Does this prove that redundancy is a complete waste?