Because implementing this doesn't change how cookie cutter it will be, no different from now.

All cashers would go a certain set of bonuses that maximizes their cash income, and pick a set of penalties that least affects them. So would all farmers, all techers etc. It still boils down to there being a "ideal set of bonuses and penalties" that can be mathematically determined, so I really don't see the benefit.

Game would just go from "you want to be a casher, you go Rep or Demo" to "you want to be a casher, you pick this and that bonus", otherwise you're a noob.

Too many choices make a game unnecessarily complicated and hard to learn.