How to Use Customer Items RATE Field

Can someone explain the purpose/function of the RATE column in the Item> Customer Details > Customer Items section of the Stock Module? I understand this section is where to input a customer’s Item Code but the Rate column seems to be unaffected by any sort of value input here. I hoped it would be to override a Price List Rate (much the way a pricing rule does on sales orders and invoices), but it does not behave this way. It seems to have no function at all. Any clarification would be appreciated. Below is an image showing an Item with a Rate that should be $7.19 but the system defaults all sales orders to the Price List Rate $6.81 rather than the Customer Item Rate. I realize that a pricing rule will accomplish the same end but then what is this field supposed to do?

Thanks,

Jammyinc
ERPNext V12