Following on from the starling thread, just to reply to this.
At the till, you also have to trust the individual to respect your privacy. We’ve seen the abuse of the covid track and trace system, where personal details have been abused by employees to aid in stalking and harassing customers they found attractive.
Second, there are laws in place to protect you from unsolicited marketing email when shopping online. You have clear opt out/in options, and you can use private relay emails which aren’t often suitable to provide verbally to another human at a till.