Most IHTSDO Confluence users do not need accounts. In contrast to IHTSDO's previous collaborative space ("Collabnet," or "TeamForge"), Confluence allows non-registered users to browse topics, delving into project spaces, without logging in. You could, for example, participate in an IHTSDO Special Interest Group (SIG) without having a Confluence login.
So why would you need an account? If you are a member of a Confluence project and you want to actively participate in that project - commenting on pages, marking off when you have completed an action, uploading documents for discussion, etc. - then you need an account.
Confluence account application forms will be reviewed by an administrator to determine whether an account is necessary for the stated purposes.