The point (heh) is not that there is no mapping between story points and time, the point is that it helps us acknowledge that these are estimates, not promises

The point (heh) is not that there is no mapping between story points and time, the point is that it helps us acknowledge that these are estimates, not promises that signify failure if broken. No individual estimate is expected to be exact, but we hope that deviations from the estimate average out across the stories in a sprint. And most importantly, story points make it easy to base our sprint commitment on the available evidence from previous sprints. We say that we can do 40 story points in a sprint, because we know that is roughly what we managed to do in the last few sprints. The conversion factor can change over time as the team gains experience, or the team changes, or the nature of the work changes. It's much harder to do such adjustments when you directly estimate hours.