All 50 states have adopted laws requiring engineers to obtain a license prior to engaging in private practice, providing engineering consultation, performing engineering services, entering into contracts, or submitting original designs, plans, or specifications for approval.
Many companies consider licensing important when assigning supervisory tasks to their employees.
Many companies consider licensing important for employee advancement along technical lines. Many city, state, and government agencies now require PE licenses for all their employees who perform responsible engineering duties of any kind. Licensing is required to be an expert witness. The qualifications required by each state are similar. There is also a certain amount of flexibility which varies from state to state.