Excuse me? Are you saying that airlines are in the habit of sending out planes with empty seats when people are waiting on standby, or with empty first class seats when people are waitlisted for an upgrade? I have flown about 100K miles per year for the last 15 years, and I have never, not once, seen this happen*. I have heard of it happening on other airlines, but it was very much a "man bites dog" level story. I would be astonished to learn that it is standard practice for airlines to turn away revenue and send out an empty seat "pour encourager les autres".
Ainamkartma
* Now, of course empty seats do happen for weight and balance issues and other causes, but to drive up future revenue by influencing customer behavior? That seems quite far fetched, to say the least.