a) It gets them free advertising by the mass media, who fall for it and quote their press release and mention the carriers' name. This in itself is a financially worthwhile reason. The airline's
PR department will be ramming it down the throats of every media contact they have.
b) People who have been burned by their carrier going bust are likely to be exceptionally aggrieved and turned off another carrier who quotes way-high fares and is seen to be gloating or benefiting from their personal misfortune. Even Michael O'Leary wouldn't be silly enough to do this.