Currently, D365 functionality is that if a business/company sells products as part of a project then there is a cost and a potential profit/margin calculated, however if the same business sells the same products BUT NOT as part of a project then there is no cost and no profit/margin.
For businesses that sell Professional Services (projects) and products together and separately, and need to calculate the profit they make whether the products are sold as part of a project or not, this is currently not possible using OOTB Dynamics.
FYI - the Current Cost and Standard Cost fields on the product have been around for years. It is just the calculation that uses them that is specific to PSA.
I cannot see any logical reason why you would want to only calculate the profit if you are selling projects. Unfortunately this lack of foresight in the development is forcing us to have to bypass the good functionality developed by Microsoft, to calculate the profit, and calculate it ourselves.