There is a need for a secular guide to spirituality because there are so few resources available on the subject.
There are huge amounts of resources available about religious spirituality: Sacred texts (Bible, Koran, Torah) and plenty of experts (Priests, Fathers, Rabbis, Imams) to speak to and plenty of religious scholars to study. And religions have large support communities and any believer is usually more than willing to have conversations and share their thoughts.
Even mysticism has plenty of resources. There are numerous gurus available, books, workshops, retreats, etc.
There is also plenty of information available about atheism. But most of it is by angry atheists and is devoted to defending atheism and/or slamming the popular religions.
There is precious little serious information available about spirituality from a secular prospective. Secular spirituality is mostly a do-it-yourself effort.