Cooks has skins in the wall....Gallup was MIA all of last year, and has something to prove before just being "penciled in" as a starter.
Gallup make steady progress his first 4 years in the league and then got hurt. He was a young 1000+ yd receiver before the injury and in the NFL that is worth the contract he got. He did not get WR1 money or close to it. He was not a flash in the pan 1 year wonder.
Injuries are an unfortunate part on the attrition league. Gallup has come back from his ACL in the usual time frame. He looks much better physically this year and is winning reps against the starting defense which is pretty good.
I don't even know why Cooks is part of the discussion. The one that he is competing for snaps with is Tolbert. If Tolbert outplays him then I can see the argument that we cannot pay a WR4 that much but that has not come to pass yet.