You may encounter a scenario where customer does not want to input a payment method and you are happy to on board the customer without one. You can disable this option in Customer Settings bye following the steps:
You can toggle OFF the setting that requires the customer to input a payment method by following the steps below:
Go to Customers -> Search for Customer -> More Actions (...) -> Customer Settings -> Toggle OFF the "Payment Method Required" setting.
Once you toggle OFF the "Payment Method Required" setting, a pop-up will come up, Click on "Ok".
Note that once you toggle OFF the "Payment Method Required" setting, there will be no drop-down options to select for "Primary Payment Method". If your customer would like to add one later, you need to toggle ON the "Payment Method Required" setting.