Because I never heard anyone refer to him as Marc Aurel in any of my philosophy classes and could not find any references to "marc aurel" on the internet. The familiarity of the statement made it seem like "marc aurel" was a household name. I also could not find the sentence in any copy of Meditations I found on the internet.

Fyi: you can grab a copy of Meditations from a number of classics sites on the internet:

http://classics.mit.edu/Antoninus/meditations.html