FDA does regulate tobacco, as well as almost everything else that we put in our bodies.
They regulate foods (except for most meat which is under the Dep. of Agriculture), food additives, infant formulas, dietary supplements, drugs, vaccines, blood products, biologics, medical devices, electronics that emit radiation, cosmetics, products for animal consumption (feeds, drugs, devices for pets, farm animals, etc.), and ... TOBACCO PRODUCTS.
"The Center for Tobacco Products was officially established to implement the tobacco control act. Among other things, the Center will oversee the regulation of the marketing and promotion of tobacco products and set performance standards for tobacco products to protect the public health." - fda.gov
There's a lot of legalities and categorization involved with FDA regulation, and therefore saying someone wants tobacco FDA regulated could mean different things.
I'm assuming that people would like tobacco products to be regulated in a different category that requires slightly stricter supervision, such as drugs. If they do want tobacco products to be regulated as a drug, the whole tobacco plant or product itself cannot actually be regulated as a drug as it's a botanical and therefore would be, if anything, a food or a dietary supplement. Nicotine would be the drug - it's only possible health benefits is perhaps relaxation (that's more addiction related, in which it is illegal to prescribe off-label use for addictive purposes) therefore there would be no efficacy for the FDA to approve of, and the only thing would be toxicity. [Off-label prescribing BTW is prescribing a medication for an indication (use) that is not FDA approved. Prescribers are allowed off-label prescribing for just about everything EXCEPT for feeding an addiction.]
The nicotine in tobacco is categorized as a drug, and although it is highly addictive, it is not a schedule drug and can be prescribed mainly for smoking cessation (it's treating an addiction, not feeding the addiction). The FDA could ban nicotine (and therefore tobacco products) by categorizing it as a Schedule I drug - this would the put it under the jurisdiction of the the DEA. People completely opposed to tobacco likely want nicotine to be categorized as a schedule drug for its highly addictive properties. Nicotine hasn't be categorized as a Schedule I because in the way that people usually take it, it's just not as dangerous as other illegal drugs like LSD or heroin. Granted high doses of nicotine will kill you, nicotine overdose from tobacco products almost never happens and is certainly much less common than overdosing on a Schedule I like heroin. I could understand nicotine being categorized as a lower schedule drug because of its highly addictive properties, but so far it hasn't been.
Tobacco could also be regulated as a dietary supplement, as it fits in the dietary supplement area of "herb or other botanical." In this case tobacco producer would simply need to be responsible for ensuring that the product is safe, it has no misleading claims, and that it complies with other laws. They wouldn't need FDA approval before marketing, though. This wouldn't do much in terms of increasing regulation.
Aside from the current status of tobacco with FDA regulation - some may think tobacco should have stricter regulations within the FDA for public health reasons. Tobacco has no beneficial use and instead only causes a plethora of health issues. They may also want to retract FDA's inability to ban tobacco products, therefore giving them the authority to outright ban cigarettes.
Note that "The Family Smoking Prevention and Tobacco Control Act specifically states that FDA cannot ban an entire category of tobacco products, such as cigarettes."
- Sorry for the long response. Drug regulation is complicated. Hope this helps though.
fda.gov, Pharmacy student (A in drug law :P)