You're confusing the fact that it hasn't happened for the idea that they aren't trying. Trades take two teams to happen, and nobody is throwing in the towel after 2-3 games. Most teams don't have depth any better than ours, so why should they give theirs up when injuries are commonplace in the league? This is just reality in the NFL.
With McKelvin, it's a thin corps but an OK one. Without him, it's a mess.
Your hands are a bit tied if you want to keep these injured players or use them later in the year. You can't IR everybody, and you can't cut them either. I suppose you could look for a guy better than Justin Rogers, but then you have to answer this: if the guy is better than Justin Rogers, why doesn't he already have a job?