By default, Clara sends calendar invites to all participants in the meeting and to your default email address.
Adding multiple email address could be helpful for you if you:
Have multiple email addresses or calendars that you use regularly, and they are not viewable/synced in one application.
Need to keep someone in the loop with your schedule.
Need to ensure a CRM or ATS is informed of your meetings, and you can share this data with the system via email (e.g. Email to Salesforce).