They're also useful in retro for the simple fact that something was written down. If your story point estimate was way off for a particular task, you can pull up the original conversation, identify what assumptions were violated or what new info was surfaced that wasn't present at the original estimation and whether there's learnings/process changes to be made.
Of course, retro is usually the first thing to go in a deluded attempt to increase velocity and story points hang on as this vestigial tail, contributing to more cargo cult software engineering.
edit: One scenario that might play out:
The team all agreed that tasks A, B & C were worth 3, 5 & 1 points respectively but Steve and Mei thought task D was worth 5 points but Carol thought it should be 13 because it involved integration of an external API where her experience was that other API integrations in the past had exposed hidden complexity.
Task D ultimately was not completed because during the process of integration, it was discovered that the API did support a key feature that was needed and instead, an in house alternative needed to be built.
It was decided that going forward, the team would instead assign a 1 point task to building a toy app for any new API integrations that would then feed into the process of deciding the story points for features requiring that integration.
Of course, retro is usually the first thing to go in a deluded attempt to increase velocity and story points hang on as this vestigial tail, contributing to more cargo cult software engineering.
edit: One scenario that might play out:
The team all agreed that tasks A, B & C were worth 3, 5 & 1 points respectively but Steve and Mei thought task D was worth 5 points but Carol thought it should be 13 because it involved integration of an external API where her experience was that other API integrations in the past had exposed hidden complexity.
Task D ultimately was not completed because during the process of integration, it was discovered that the API did support a key feature that was needed and instead, an in house alternative needed to be built.
It was decided that going forward, the team would instead assign a 1 point task to building a toy app for any new API integrations that would then feed into the process of deciding the story points for features requiring that integration.