Why are civil engineers often employed by the government?
Civil engineers must first gain experience working for the government in order to be accredited.

Governments are usually responsible for building and maintaining the built environment.

Governments must hire civil engineers because they cannot contract with civil engineers directly.

Private businesses often do not have the resources to pay civil engineers’ salaries.

Public works, which are the responsibility of Government, generally have a considerable civil engineering content. Government employs civil engineers to propose, design, and oversee the construction of such projects.

In some cases, the government employee simply needs to be knowledgeable enough to understand the work done by the contractor's engineers. In other cases, the government employee must make sure the contractor's engineering work is accurate and complete, makes use of appropriate technology, and is in compliance with appropriate regulations and standards. That can require educating the contractor--more than simple oversight.