Customer records are stored in order to support a number of Vivamo services. Ranging from storing payment methods, through to fraud/AML monitoring and more.
You can retrieve a full customer record, including their stored payment methods using the Get customer endpoint. This will give a 404 if the customer does not exist.
It is possible to create customer records outside of a payment flow. Note that a customer can be created with minimal information to begin with, but further updates can be made to add extra required data (payment methods require varying levels of data).