What is the primary purpose of adding a payment service to invoices in Xero?

The primary purpose of adding a payment service to invoices in Xero is to get paid faster by enabling a "Pay Now" button. This feature allows customers to conveniently make immediate payments directly from the invoice they receive, which streamlines the payment process. By incorporating a payment service, businesses can reduce the time spent on following up for payments, increase cash flow, and improve overall customer satisfaction.

While the options about viewing outstanding bills, applying default due dates, and customizing email templates have their own purposes within invoicing, they do not directly address the primary goal of facilitating prompt payment through a streamlined mechanism that the "Pay Now" button provides.