Telling someone they can't have something makes them want it more

Psychologist Jack Brehm proposed in 1966 that when people feel a freedom is being threatened or taken away, they experience 'reactance' — a motivational push to reassert exactly the freedom under threat, often by doing the forbidden thing more, not less. It's why banned books sell better and warning labels sometimes backfire, and it's a core reason heavy-handed persuasion tends to provoke the opposite of its intended effect.

— Jack W. Brehm, A Theory of Psychological Reactance — Academic Press, 1966