It is not necessary for participants to have Poll Everywhere accounts to participate in polls or surveys. However, It is necessary for participants to have Poll Everywhere accounts if you wish to export grades from Poll Everywhere to Courseworks (Canvas) or to manage participants in groups/courses.
Keep in mind that in order to export grades from Poll Everywhere to a Courseworks (Canvas) course you must select "Restrict to registered participants only" at the time you create the poll.
Note that It is still possible to have polls with anonymous responses even when completed by registered participants.