Think of your Email Campaigns as a folder that you group similar emails in. You do not need to add an Email Campaign each time you want to send an email.
Organizing your emails into campaigns can better help you understand your reports. For example, you could have your monthly newsletter sent every month from the same Email Campaign and be able to see your user engagement month to month.
It’necessary to separate and organize your emails into campaigns so that you can keep your content in order. This way, it’s easy to find the email in your reports. While also being able to understand your user engagement better.