There's no doubt that Bell and Donald are both the top players at their positions and deserve contracts befitting of that distinction. However, the Steelers seem content to let Bell reassert himself under the franchise tag, which Bell has yet to sign. The Rams have been intensely negotiating with Donald, but have yet to find any common ground.
These situations tend to get more serious once an actual training camp holdout is involved. Thankfully, both clubs are more than a month away from that benchmark.