If you're sending a file on a schedule, they do not need an account. The email arrives in their inbox with the report as an attachment.
If you're sending links where they access Workspace in the UI, they require an account. This is part of the 'Share Project' feature in Workspace.
If you want to send reports to individuals that don't have an Analytics login, use the Send File on Schedule feature.
If you want to send reports to individuals that already have an Analytics login, use the Share Project feature.