Why not just fire them or cut their pay? As you may know, ESPN just suspended Bill Simmons for three weeks.
One possibility is that a fined but still active worker may continue to “shoot off his mouth” and thus increase the ongoing collateral damage. (Simmons called the NFL commissioner a “liar” and I believe he works for one of the network’s revenue sources.) The suspension is a kind of cooling off period.
Another possibility is that ESPN wishes to shift the long-run bargaining equilibrium. They wish to signal to Simmons that he isn’t as valuable to them as he may think he is, in the hope of either cutting his pay relative to trend or inducing him to be more careful with his future words. They wish to show they can go without his output for three weeks, without (perhaps) a major loss of business. Fining him would not shift the long-run balance of power in the same manner because ESPN is continuing to rely on the traffic which Simmons brings in and thus signaling that they really need him.
I do not know if the suspension is with or without pay, but a version of the above argument can work either way, with some modifications required.
If I were the commissioner, I would be insulted by the suspension of Simmons. It suggests these are words which cannot be said, perhaps because they will elicit audience assent. The suspension also signals that ESPN regards the commissioner as quite thin-skinned and presumably — especially if he is indeed thin-skinned! — he could be offended by that too.
In sticky nominal wage models, it remains an interesting question why more workers are not suspended rather than fired outright. Indeed this used to be closer to the norm in many manufacturing labor markets.