A new part/drawing/assembly in SolidWorks always starts with a template. Whenever someone first installs SolidWorks, default templates get created. Because those templates contain the default planes (and a few other features), those features will appear to have been created by the original user.
You can create individualized templates for every user (I cannot imagine a scenario in which this pursuit would not be misguided) by closing SolidWorks and moving the original templates somewhere else. When the new user starts up SolidWorks, there should be a message that SolidWorks cannot find the templates and that they will be created. New templates will be created with planes that appear to have been created by the new user.