Or, they can put in some 'junk' items in the reward of other crew skills for vendor.
Or, they can lower the cost of other crew skill missions.
Or, they can increase the vendor value of the other crew skills craft items.
To be honest, so far most of my credit comes from useless junks, not slicing (due to failed mission).
Having slicing as a crew skill is like not having another credits-sinking crew skill - it saves your credits, not necessarily earn them.