While the development and QA servers are by definition not customer facing production servers, they are in fact production servers to some. In this case they are production servers for your Development and QA teams. Because of this I always recommend backing up development and QA servers to my clients. The dev and QA teams aren’t able to work without their respective servers, and if large amounts of data change are lost from the dev and QA databases then that data or schema changes will need to be identified and reapplied which takes time and resources costing the company money.
Because of this I always recommend that these systems should be backed up just like the customer facing production servers are.