It's probably because research on presence is still a topic of research. You could start with one of Mel Slater -who work on that topic since the 90ies- last paper:

Article Simulating Virtual Environments within Virtual Environments ...

Thanks for the tip, Cedric. The psychometry of measuring presence appears to be problematic for VR reearchers. We appear to know "presence" is and to recognize it when we see it, but not yet to understand how to mesure it precisely or exactly how to ahieve it. Very interesting issue for research in virtual environments.

The question is a bit dated, but since I just stumbled upon it and there are still followers to this: You could also take a look at the IPQ, a questionnaire on presence (see attached link).

It is being used actively by several groups working in the virtual reality domain, as seen recently e.g. at the ACM VRST 2016. 

http://www.igroup.org/pq/ipq/index.php