Taxes reduce consumption and usage of the products being targeted, it is just often the case that it isn't reducing consumption among the people being targeted.
As a way to spur consumption of 'healthier' eating, societal food advocates have sought to tax sugary drinks. A paper by RTI International, Duke University and the U.S. Department of Agriculture instead finds that heavier taxes on sodas and juices is simply creating a government subsidy for other unhealthy foods - the reduction in sugary beverages due to a soda tax would likely lead consumers to substitute those calories by increasing their calorie, salt and fat intake from untaxed foods and beverages.