Maybe this topic should be merged with the Reolink App topic or you should ask the question in there so the developer can respond to the question.
I can only guess: Wanted to include it originally, but couldnt get it functioning (yet).
Originally Reolink camera’s don’t support facial recognition because of the privacy concerns
Note : Facial recognition security cameras can possibly cause privacy infringements and data security risks, as they capture and analyze individuals’ facial features and personal information. As a responsible security solution provider, Reolink consistently prioritizes user privacy. Consequently, Reolink cameras do not currently offer facial recognition capabilities . However, you can utilize alternative features, such as person or vehicle detection, to meet your needs
