I asked that same question, only in so many words. Here is a couple answers I received.
I was talking to a lady in a chat room who said she was isolated from the city. Her family was not religious and the only way she knew God was from the Bible. So, when I asked her to back up her own thoughts in her own words she could not because all of her thoughts on faith rested in the only text she depended on, scripture.
While another person who does not back up his scripture quoting by any wording of his own, continuously believes the more people hear (or read) his Holy Book somehow they will somehow understand the context to which
that person is speaking (or knowing his point when he posts scripture)
Even if it is not backed up by "reason" that everyone agrees with, their opinions at least should be backed up with their own words. For if the prophets, disciples, and apostles can talk without their Holy Book to others, why can't we?
Also, many define reason differently. My friend believes that God is common sense. She cannot function or see objective reasoning because to her, God is all there is and all that exists. So, sometimes it's just people of faith it's not that they don't want to step out of their box, it's because they can't. That is all they know.
Our reality is all we know. We used to think the world is flat and now we know it's round. I guess we need to accept people where they are and hope they are nice about how they come across when quoting their faith rather than discussing it.
I have noticed a new trend amongst religious reformists. When they bring forth often radical or heterodox opinions they always try backing it with their religious text that is the core of their religion. The issue is that very few progressive ideas have any place in many religions. Homosexuality, peace, or even marrying a person outside of one's faith is disliked by many religions.
Why is it that the religious can never back their assertions with reason instead of appeals to a holy book? Is it that the religious are intellectually bankrupt that they cannot be reasoned with?