If you practice allegorical interpretation, you are in effect saying that the text doesn't really mean what it says; so what incentive do you have to faithfully preserve it.
If you believe in direct inspiration, and take the text literally; there is a strong incentive not to tamper with it.
When 2 chronologically older MSS from 1 place, that practices allegorical interpretation, disagrees with more than 8 MSS from 5 different places, widely removed from one another, where literal interpretation was practiced; I believe the geographically separate texts in agreement are more credible.