Why would this be different?
You don't get it?
Because we're not talking about the captain, gunner or cleaner of a ship. We're talking about people playing a game in their free time. They have options and all of their time has the same value. By giving them ingame paycuts based on role in a cooperative activity, you discourage cooperation.
Free time is the most valuable player resource. Players may chose how to convert that into ingame things. Fun, fooling around, rank, credits. If you present them with something like Wings has been for the longest time ("yeah, play together if you will, but you will greatly slow your ingame progression") and an alternative that does
not gimp credits, you clearly don't want them to engage in the gimped activity too much.
Humans min-max. Not everybody, all the time, but they will do.