Example, got a feature with a new required field? Add empty field, synthesize a default value for existing rows, start accepting data, validate that data, require the data, use the data.

If you’re doing deployments once a week, you end up juggling two stories so you’re not sitting on your hands the whole time, and two stories divided your attention, so the odds of fucking it up go up anyway even though you’re being careful on paper.

Meanwhile one of your coworkers is doing the same dance on another feature, so you start tripping over each other as team size increases.