The "customer reference" field is mostly used to store historical references from previous software.

If you need a similar mechanism in Odoo to improve the customer relationship, I would use the "id" field (of "res.partner" object). It increments automatically as you create new contacts (1 -> ...). You can add it to the email using placeholders, you can display it in the printed documents, you can type it in the URL to directly open the related contact form when interacting with them, or even use it in quick searches of search views.

You can find an example of this in the Helpdesk app. Ticket ref is the record ID.