Part of it is the personal appeal of the Christian message of community, service and selflessness. Part of it is a personal feeling of spirituality and connection to people and the universe. Part of it is certainly cultural, if I'd been born in a Muslim country to Muslim parents I don't see any reason why I'd be anything other than Muslim myself, but then I'm ok with that. Same goes for Judaism, or Hinduism. My faith is a completely subjective experience, I don't give it objective weight or feel any need or desire to push it on anyone else. In that sense I'm a secularist.