We use the phone number at check out process for any one of these three reasons:
1) verify that you’re a real person. There are a lot of ‘bots’ that create fake accounts on sites like ours. If we have a phone number we can manually verify people if needed.
2) occasionally, customers register and accidentally type in the wrong email address. We need another means to contact customers in case this happens. We need to talk to these customers on the phone when this happens.
3) depending on how customers place an order (credit card through our credit card processor, or PayPal or PayPal e-check) a phone number is required for verification.
We don’t use the phone number for any other reason.