[nxc18]

Not defending United, but the airline industry is known for having pretty slim margins.

Air travel is fantastically expensive and we all want it to be cheaper than it really is. This is one of the ways that is done (people who don't show up pay for other people and displaced passengers move to underfilled flights).

The practice is annoying, but I think with the exception of bungled reqccomodation is a net plus for the consumer.