Again

On first glance, this makes no more sense than it ever has.

Two Westerners beheaded by Islamic State did in fact generate the expected response. President Obama has proposed direct attacks for the purposes of destroying them. Why do it again?

Granted that there is no reason to pretend they are going to go along with the United States or anyone else who doesn't like their methods to date. They could hardly be expected to be contrite, nor would anyone else have a reason to believe them if they were. That is, there's no reason for them to change anything about their actions, because no new information has been generated: The U.S. still doesn't like what they are doing, and Islamic State still has no reason to stop.

In fact, one interpretation is that this execution is a response: Message received. Attack if you want, we can kill, too.

It appears, though, there aren't many better reasons to explain it. Perhaps it's still a recruiting tool. Those might have required some additional oomph after it becomes common knowledge that anyone in the organization could be nailed by any of several U.S. launched guided weapons.