When Richardson gets injured, and we have problems moving the chains because none of our WRs besides Baldwin or Lockett can get first downs for us - just remember your concern.
Keeping Alex Collins cost us 2 games last year. It isn't out of bounds that keeping a worthless WR that can barely produce against the 2s might hurt you in real games. Not just a WR issue either, Desir losing a roster spot especially, because he is a serviceable CB that we are very likely going to need if any of our secondary goes down for a few downs or a few games.
When we continually have problems scoring in the RZ because we need a big bodied WR and because our OC is too stupid to figure out how to use Graham, just remember you pointed out that keeping Darboh won't matter. Keeping a worthless player takes up a roster spot that a player that could have contributed could have had.
Not getting those contributions can lose you games, especially when you lose a starter for a few snaps and need players off the bench to step up.