For the reason mnehrling stated. But also, 1:14 says "And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years"
So not only does 1:14 speak of the creation of the sun and light, but also explicitly recognizes (in the last clause) that the days could not be divided before then.
Gen 1.14 says "lights" ... not light. Light was not created in Gen. 1.14 ... it was created in Gen 1.3 "Let there be light". Please read the text.
... but also explicitly recognizes (in the last clause) that the days could not be divided before then.
It says nothing of the sort ... read the text ...
4 God saw that the light was good; and God separated the light from the darkness. 5 God called the light day, and the darkness He called night.
The text in Gen 1.4-5 explicitly claims that GOD did the separation of the days prior to Gen 1.14. God separated the light (day) and the darkness (night) in verse 4. It also states that the concept of a "day" was defined BEFORE the creation of the sun. Evening and morning ... evening and morning ... evening and morning ... then the sun ... evening and morning ... etc.
All that we can understand from the text of Gen. 1 is that God created light, HE separated the light (day) from the darkness (night), and that evening and morning marked the beginning and end of a day. Then after the sun was created, the SUN separated the day from the night.
So you have a progression like ...
Day 1 - God separated day/night
Day 2 - God separated day/night
Day 3 - God separated day/night
Day 4 - Sun created to separate day/night
Day 5 - Sun separated day/night
Day 6 - Sun separated day/night
Day 7 - Sun separated day/night
etc ...
When someone comes up with a foreign interpretation for a straightforward passage, I always wonder if there is an underlying theological problem the new interpretation is trying to solve.