You must mean some other "they", as our government has a much easier time finding ways to perpetuate taxes than they are willing to wean themselves from the revenues tobacco brings them... approximately 156 billion $ since 1993. They are not going to suddenly place onerous, confiscatory taxes on food substances that cannot be separated from the most common and popular foods consumers buy, and which support whole food industries that generate their own vast tax revenues already.
The Federal government continues to subsidize tobacco farming to the tune of millions... "Tobacco Subsidies in United States totaled $528 million from 1995-2004." Is that a sign that they will prohibit smoking any time soon? The Feds are investing in a cash crop. This is a fraud, and many people are fooled by it, thus we see the same kind of political demagoguery displayed every election cycle, yet the status quo is as solid as ever.