I think it is a mix....those confined to their respective religions have a bias that they have issues getting beyond, whether you are dyed in the wool, Muslim, Hindu, Christian, Buddhist or whatever you are married to your belief, your books, your mentors and will have issues looking out of the box....in just the beginning of every conversation you would just so much like to 'save' the other, get them to 'see' the light, and 'understand' the 'truth' as you know it.
We are all in the same boat..... I'm there too, so is the Atheist and Satanist, so we really should learn to get along....
But as I see, it and I may as well get this out before you toss me to the sharks... Spiritual is what we WERE as individuals....then someone decided to write down their interpretation of the discussions they were hearing or heard as a child, and someone else wrote down their understanding, and others disagreed in whole cloth or on some principle or some nuances so their stories circulated and were written... It may have begun with power and greed in mind...or it may have begun with the insistence that their story be recorded as they knew it or it could have been without and malice or forthought....
regardless, has been warped over the years, centuries....and is not without original intent....but one needs to look past a lot to find it.