Edgerin James had the best quote on this a while back. “ I only went to college for 2.5 years but I know what voluntary means”
The players only hurt themselves in the long run by shortening practice times every chance they get including in the CBA negotiations. It's the only thing they ever fight for when they should be pushing for expanded rosters, practice squads, eliminating the franchise tags, etc. The less practice contact you take and less football related activities you do, the more susceptible to football related injuries I believe you will be. You can run on the track all you want, but even in shorts, pads and a helmet, there's no simulating a football cut in the heat of a play with your local trainer.
Well, they can't be because they are doing precisely what the CBA says they can. What should they be fired for?