Happy to see this question.
It's about scalability. A developer sitting with a laptop has the potential to effect more changes in revenue than a salesperson. This difference is especially massive in lower and mid level roles. As you go up the ladder, sales and marketing roles pick up speed and to be specific, CXO roles in Business and Product are paid equally in most sectors.
Example of scale: A developer deploying an app feature for push notification has the potential to change the revenue across the entire user base of the app. A sales person who is dealing with a customer (B2B or B2C) has potential to only get that 1/10/100 orders at maximum.