Why does Siri store your interactions

Hi. This article describes data that is stored by Siri and how it uses your responses to improve https://support.apple.com/en-gb/HT210657 Siri is designed to be secure with privacy in mind, so any of your Siri interactions will not be identified back to you as a unique and random identifier is used to send data to Apple

Apple saves your interactions with siri in order to improve future user experience!

you can opt out of this by turning off Improve siri and dictation in Settings>Privacy>Analytics and Improvements