This site sells ebooks. You download them. I won’t physically mail them, let alone bring them to your house. Why the heck do I request your address and phone number in the checkout process?
Because the commercial, off-the-shelf software I use (WooCommerce) asks for it.
Yes, I can disable this. But that means maintaining local patches against WooCommerce. And every time there’s a WordPress or WooCommerce update, I would need to re-validate those local patches. And every time I need to open a trouble ticket with the vendor, I’d need to remove those patches to get support.
I don’t check either your physical address or your phone number against anything. I care about your PayPal transaction.
At such time as I decide to process credit cards, this will have to change.
Note that if you need an invoice for business or tax purposes, be sure that your address is correct. You can print an invoice for your order from your account.