Taxing something almost always decreases usage. By how much depends on the rate and the elasticity of demand. Gambling demand is probably very inelastic, much like cigarettes and alcohol. (Your argument supports this too) If the rate is low too I can see your point about not having much effect. But it still has an effect. Excessive sin taxes can be the sign of a nanny state, but otherwise I agree with it. All taxes are bad anyways, some are just less worse.