I have met people who are religious, as in they go to church and read the bible, but they aren't necessarily philosophical. They don't question things or search for answers (which to me is the basis of philosophy) and believe what they are told. Therefore even though some philosophers use religion to back their theories and their beliefs there are many that are atheists,but do they still read the texts of religious philosophers? Philosophy and religion are both topics that cannot be determined by concrete evidence, so while they are similar they also have their differences. It's the same with being spiritual, there are spiritual people who are not religious. The problem is people automatically assume that a spiritual person is religious and vice versa and it's not always true.