I worked with a mid sized contractor whose project schedules looked solid on paper and fell apart the moment weather, supply, or labour shifted even slightly.
1, A single weather delay on one trade quietly pushed back every trade scheduled after it
2, Change orders triggered by delays were discovered weeks after the cost had already been incurred
3, Static spreadsheets could not account for how one variable affected every other variable downstream
I worked with a multi location retailer that was excellent at marketing demand and consistently bad at predicting it.
1, Their best selling items sold out in some stores while sitting unsold in others
2, Overstocked seasonal inventory tied up cash that should have gone toward what was actually moving
3, Store level reordering relied on manager intuition that varied wildly from location to location
I worked with a manufacturer who treated unplanned downtime as a cost of doing business, until one bad week proved how expensive that assumption actually was.
1, A single unplanned line stoppage was costing more in lost output than a full year of preventive maintenance
2, Quality issues were caught after the batch shipped instead of before it left the line
3, Adding more inspectors slowed the line down without actually catching more defects