User Stories are not requirements

Treating user stories as requirements may not be too different from asking users to estimate how long it takes to do their tasks and using those estimates as your project estimates.

Santayana

Those who do not remember the past are condemned to repeat it.

Those who are not aware of the past are condemned to repeat it.

History repeats itself because the past is not the dead past but a mirror (albeit incomplete) of the very much alive present and future.

Battle Success vs Project Success

Every battle between armies results in success for one side failure for one side. There is a winner and there is a loser (ignoring ties). That means 50% of battles are a success, and 50% of battles are failures. 

In contrast, 60-70% of projects fail (according to popularised stats). 

In other words, armies do better at succeeding against obstacles that ACTIVELY aim to LITERALLY devastate and rip them apart, than projects do against the comparatively passive triple constraints.   

(I know there's fatal flaws in this argument, but still).