Everybody makes assumptions. No-one ever makes a decision for which they might be accountable. All decisions are made for short-term gain. People never talk to each other. It is the nature of machines to break.
Data communications have an infinite number of ways to fail.
All mistakes are repeatable. The highest standard that a move can ever achieve is to be unremarkable. Every interface or separate responsibility multiplies the effort spent in politics and communication. Nobody ever listens. These may look cynical, but you can bet on most of the Bad Thirteen happening.