I don't know why United didn't just offer more compensation for passengers to give up their tickets.  $800, a room, and a meal pales in comparison to what Delta is willing to pay.  check out this Forbes article on this family that made $11,000 for giving up a series of tickets.  

 https://www.forbes.com/sites/laurabegleybloom/2017/04/09/why-delta-air-lines-paid-me-11000-not-to-fly-to-florida-this-weekend/#664a74de4de1