Not saying it's right, mind you
"Chipzilla's marketing department hired her right out of college as a customer service analyst. From there, she worked her way through the marketing department to become a field sales engineer for the sales marketing group."
This was the explanation. Anyone who has worked for large corporations knows that the salaries of people who work their way up from "lesser" areas are rarely brought up to the level of people who joined the group with an appropriate degree.