Earlier quoted context omitted.
No mystery. Behavior converges to incentives: * You do get academic points for chairing a conference, and as a chair, you do need to find reviewers. * A colleague is running a conference, and asks you to do a favor. You want to help your colleague. Reviewing papers wins you points with them, and declining to review burns bridges. When you're running a conference, you'd like them to reciprocate. Plus, they might be on…
> Reviewing papers wins you points with them, and declining to review burns bridges. When you're running a conference, you'd like them to reciprocate. Surely they'd get upset if you rejected all of the good papers, thereby ensuring that they would have a bad conference.
If there is space still left at the end you can look at the others and take the first paper that looks fine until there are no spots left.