When do you not need to create a user persona?

I was wondering when do you not need to create a persona? I see examples of redesigns of existing websites where no personas have been created and instead, rely on user information generated from google analytics.

I understand that the benefits of personas are to unify the team to think of solutions for the user and to help focus solutions and align your information architecture with what they are most wanting to find on the site.

However, do you only need to have personas on new products that are starting from scratch? Is it not beneficial to have personas for any type of process?