(One of the reasons) why marijuana is still illegal

This nation smokes far more pot than uses any other illicit drugs. For example, almost half (47.8%) of all high school seniors tried it, as compared with the next runner-up - all of hallucinogens, at 12%. Source: Monitoring the Future Study (2002). The numbers are similar for general population drug use - marijuana users represent an overwhelming share of drug users in general.

This information generally requires no specialized knowledge. Similarly, by now it has become apparent to the point of becoming common knowledge, that the dangers of marijuana smoking are seriously overstated, to say the least. Some even call marijuana "the safest therapeutic substance known to man." Who?? None other than Administrative Judge Francis Young of the DEA in In The Matter Of MARIJUANA RESCHEDULING PETITION (Docket No. 86-22). It is very likely that even the most stalwart DEA officials don't really believe in the dangerousness of marijuana.

So, how come it remains in Schedule I?

The answer lies in the first paragraph. Removing marijuana from the list of "evil" illicit drugs would substantially reduce this nation's drug problem: without marijuana the number of drug users - other drug users - would drop significantly. A dramatically smaller drug problem wouldn't justify tens of billions of dollars in funding that the DEA currently receives. Regardless of the objective pros and cons of marijuana use, the DEA will always oppose the rescheduling of marijuana simply because they want to retain their allowance.

In order to request an addition, deletion or a change in the schedule of the drug, one must petition the DEA. When a petition is received by the DEA, the agency begins its own investigation of the drug. Then, the investigation goes through some more motions, until the DEA Administrator reviews all available data and makes a final decision whether to propose that a drug be controlled and into which schedule it should be placed. I wonder how objective you would be in making a decision that has a potential to deprive you of a substantial majority of your budget?