Eliminates influence

The absence of a joint session eliminates any inadvertent influence on the study participant by the UX researcher. The validity of the data could be compromised by as subtle an influence as a sigh, or obviously taking notes, for example. Moderating a usability study requires a skilled moderator who is experienced enough to know when to jump in and when to hold back. Remote unmoderated studies can be run by UX researchers who do not necessarily have this experience.