For example, there will always be a need and demand for technical documentation, engineering, legal writing, etc, all of which will and must exists without copyright. A lawyer's product is specific to his client, and bridge engineers' output are a correctly designed bridge.
You can extend it to musicians and artists. A musician get paid to play gigs at wedding, or artists being commissioned to create works for their patrons.
Copyright enables certain business models and change the quantity and quality of the work available, for ill or good but it isn't strictly necessary and may even be detrimental.