Spending time around 'spiritual but not religious' people, it's been my observation that most of them are only trying to figure out how to be as sane as possible. It is like self-psychology, with idealism and poetic wording thrown in.
Believing in a higher power isn't good enough? Next thing you know, that option is going to be removed because the religious don't believe in spiritual without religious.
It starts with spiritual and when the contracts are signed, the ceremony, the parades, the buildings with the gilded frames are built, the property investments start, the politics begin is it than considered religious.