Yes often taxation of unfavorable products would directly lower the buying incentative. But with all addictive substances it is not this easy.
Discussion
Or the government should just go away and stop meddling. They already do subsidize certain foods and now that distorts the entire market. Try to buy any packaged good at the store that doesn't have corn in it for example.
As long as you let the government pick winners the winners won't be healthy food options they will be food options with the best lobbyists.
Alcohol, legal. Weed, Schedule 1.
Corn, subsidized. beef, constantly demonized.