Good question, I guess I never really wondered that before.  Perhaps the
band and fans just don't like to be labeled?  I know Creed has a lot of
non-Christian fans in addition to Christian fans.  Also, Christian bands
allegedly have an "agenda" - to convert the people who listen to their music
to their beliefs (or to strengthen those beliefs), and Creed probably
doesn't like being accused of trying to sneak their beliefs into other
people's heads.  In my opinion, Creed's music inspires the listener to think
about the meaning behind the words, but doesn't shove religion right in your
face like some Christian bands can do.  Just some thoughts, I could very
well be wrong...  
Tara