I don't think revealed preferences are the only reasonable way to define "preference."

To use an extreme example: Does the homeless alcoholic divorcé really prefer to be homeless and divorced?

For a more abstract example, consider games like the Prisoner's dilemma, where "both defect" is worse for both players than "both cooperate" but choosing to defect always improves the result for a player. Surely both players would prefer the "both cooperate" solution to the "both defect" but without some external force, they end up in a globally suboptimal result.