yes of course they could easily mention this but that would reduce their chances of finding pax willing to accept a VDB. So of course they don't mention it.

This thread got me thinking, what percentage of VDB's go unused by kettles? I would venture to say as high as 20 or 30% go unused or forfeited.

To a kettle who accepts the voucher thinking "oh great I can use this next time I go to ____" And then by the time that comes around they forget about or it's expired or AA/UA has a better fare. All kinds of things happen that would cause vouchers to go unused.

Delta claimed fraud in changing the rules and yes there was some of that. Just a few years ago, I personally purchased vouchers from resale sites for less than face value as people were selling vouchers that expired soon and had no use for them. So the seller got some cash that would have otherwise gone to DL and I use their voucher. so DL was cheated out of the money. With the rule change, now the passenger gets cheated rather than the airline. All is fair in love and air travel?

So I get why Delta has these rules in place, but how long will this last? All these restrictions and rules and exceptions and blah blah. Soon enough pax are going to start refusing VDB's and it will be tougher to manage an oversold flight. DL starts paying out 1-3 IDB's per flight and they'll change their tune. Just wait..