It's too easy to grow excellent pot. The tax revenue would be nonexistent.
The tobacco companies already got hit for billions in legal settlements. I doubt they'd be anxious to do that again by manufacturing marijuana cigarettes.
"b) crime would be reduced"
Well, yeah. But you can say the same about prostitution. Or theft. Or cheating on your income taxes.
No too many people are robbing liquor stores to get money for their next joint.
c) less people would be put in prison with non-violent natures"
Keep in mind that almost all of those in prison on drug charges are there for dealing drugs, not using them. Legalize marijuana and they'll simply deal another drug and end up in back in prison.
"d) the DEA could focus on more 'evil' drugs."
99% of marijuana arrests are made by local or state police. The DEA (actually the ONDCP) is focusing on the borders and on drug education.
I was wrong! We disagree more than I thought. I'll use the letter system.
a) Many pot smokers are lazy and would buy it from a legal seller. New companies would arise, besides the tobacco companies to sell pot. Growing good pot is not that easy. Location and weather are very important.
b) Illegal transactions themselves are a crime and often include other criminal acts such as gun usage.
c) Fortunately, pot possession laws aren't as harsh now. However, some police do use pot laws for harassment and unwarranted searches. Just like pot users, most dealers would not move to harder stuff. Pot dealers are usually of a different nature than cocaine dealers when it comes to violence.
d) They don't make it a high priority, but the DEA does deal with pot. Maybe I should've mentioned CAMP, California Against Marijuana Producers. Mucho bucks for the war on drugs is dedicated to pot. Have you heard of how they swoop down from helicopters on suspected pot lands, detected by heat-sensing photos, with machine guns ready? I know of land owners being put in jail for pot grown on their property without even knowing it was there or OKing it. In NoCal there's an epidemic of this. Unethical growers use other's private and public lands for their plants and even put up booby traps that endanger others. I would like to see these criminals go to jail. Pot laws usually don't get these guys, and may actually increase their number.