You missed out on one of the oddities of the American government system. Since the CFTC was created initially to look at futures, and since many futures are for food products, it derives a a certain amount of its pmandate from the Department of Agriculture.
Congress also has a bad habit of jamming totally unrelated things into a bill so that members have to vote the whole package up or down. It makes it simpler to pass something if there are some goodies for each state and congressional district lumped into an unrelated bill.
I recommend drinking some USA made grain alcohol before pondering this too closely. Of course, that will get you involved with the Department of Agriculture as well as the BATFE. Why explosives and firearms are regulated by the same bureau as alcohol and tobacco is another one of those things where I recommend a stiff drink before exploring the finer details.
