Dummy salary basis

Summary:

If employees are paid cash amount only, or hourly rates provided via payroll, do we still need to have a dummy salary basis?

Content (please ensure you mask any confidential information):

Some employees and nonworkers are paid fixed cash amounts only, or hours x rate with the rate being input against payroll elements, i.e. there is no rate of pay to be held against the assignment.

1. I've heard that if the Recruitment module is used then that requires a salary basis, is that right?
2. Are there any other reasons to have a dummy salary basis, as opposed to having no salary basis there at all?