The reason people usually give for taking the beginning of Genesis literally is that that is the most natural reading. I’ve explored elsewhere why that seems like a strange way to approach it. Here are some other thoughts. I’ve tried to understand why people prefer to start with the natural interpretation, and have run across three distinct perspectives.
The first seems to be fear of over-spiritualizing. Many times over the years, Scripture has been interpreted incorrectly, assigning too much spiritual bias to it. Because of those mistakes, it’s easy to come to the conclusion that spiritual interpretations should be avoided entirely, unless specifically indicated by the Word (such as with a clear prophecy). I’m not sure what the Biblical justification is for this, though.
A second reason is the preference of rational thought to discern truth. This is at least partly as a result of the success that rational thought has had in society, as exemplified by science. As a result, we assume that correct understand is best, or perhaps only, achieved through human mental effort.
A third reason is political history. In America, the rise of the democratic model led to some minimization of hierarchical religious structures. This led to a democratization of Scriptural interpretation. Without a related increase in religious education, this led to a preference for the most basic interpretation of passages to be preferred.
The common theme in all these is the rejection of spiritual insight when interpreting Scripture. However, seeking spiritual perspectives does not mean rejecting rational treatment of it, but places such activity in a partnering role, rather than superior. For example, rational analysis can be helpful in testing one’s spiritual insights. Such a role allows both mental and spiritual perspectives to work, rather than ignoring either.
Maybe it would be better to seek a balance in perspectives, to remove fear as a motivation, and to recognize rational thought as a partner in seeking wisdom, but not the sole means of finding truth.