When I worked at a place with such a rewards program, the amount of people who put in their number/signed up for rewards was included in our performance metric. It’s so fucked up, because it impacted how many hours we were given. Never mind that if someone only works part time their numbers will naturally be lower than those who work full time, making it a self-perpetuating cycle for those who want to move up to full time.

Anyway, point is - if the cashier cares, it’s because a messed up system is compelling them to. Which is why instead of saying I don’t have an account (which will prompt them to ask me to sign up), I just use Jenny’s number.

True but giving a phone number often gives discounts... Giving a fake number like 867-5309 doesn't compromise your privacy at all.