I guess I should butt into this argument, as a former pothead from a long line of potheads. Yes, I'm admitting to crimes on the Internet, oh how brazen of me.
On "gateway" drugs - In all the times that I smoked marijuana, I never once thought it'd be a good idea to try something harder. None of the people I ever smoked with did either. My father, who's been a proud pothead since 1971, tried cocaine exactly once in all that time and was so revolted he never touched it again.
Arguing that marijuana should be wholly illegal for safety or health reasons is completely hollow unless you also think alcohol and tobacco should be wholly illegal. There's no reason why it can't be treated exactly the same way, and the only reason it's not is because dope never had an industrial basis on it's side like alcohol and booze.
Arguing that it would create crime problems is pointless, because the very fact that it's illegal now is what keeps it embroiled with the criminal element. As Alcohol Prohibition proved making something illegal puts the industry of it in the hands of people who would break the law anyway.
Arguing that it would spread marijuana use (won't someone think of the children?) is ridiculous. You can already buy pot at corner stores just like beer and smokes, it's just not on the shelves. There's no one out there thinking to themselves that they'd smoke pot if only it wasn't against the law. I'd be will to say that legalizing pot would slightly reduce it's usage, because without the "risk" of illegality, it wouldn't be as hip and cool and counter-culturey.
As the Californian lobby points out, it's the biggest cash crop in the state at $14 billion, surpassing California's oranges and vineyards. The same story goes for another half dozen states. There's every reason to let it be a legitimate industry like any other crop.
The typical drug pusher however, the guy who stands out on the street corner to sell you crack, earns less per hour then working at Micky D's (which he might very well do as well.). They're in it for the hope of being the boss one day, they get paid like shit. The runners make even less.
I don't have a lot of information on this, because asking a seller about his business is extremely bad form, but the guys I've dealt with had fairly reasonable incomes from pot. Some did it as a supplementary thing, some as their primary business. But not one of them ever had any aspiration of being a bigwig crime boss or Hollywood crap like that. I think you've got a slightly distorted picture of the drug culture from movies and TV. Every guy I've dealt with was middle-aged whitetrash just selling dope like any other job.