What's Behind the Quest to Legalize Pot?

Now that gay marriage is out of the way, the left is making the pivot to a legalization of marijuana as the next cause celebre they intend to push.  And massive inroads are being made: multiple states are putting forth "medical marijuana" initiatives, and Colorado in particular is looking to "Amsterdam" their whole state.

I don't want to argue the medical benefits of marijuana - I know there are some folks that can be helped by it, and I'm in full support of that use.  I also don't want to get into the stale arguments of the virtues of pot over alcohol.  Those arguments are all over the web, and the debate is tired.  

Instead, I want to understand why there is this push.  Why, of all the things politicians could focus on, why this?

I've had and have friends that smoke a lot of dope.  Still - into their 50's.  And based on that unscientific observation, here's what I've found:

• They never achieved the promise of their intellectual gifts.  They were slowly robbed of their wit, humor, acuity,  and ultimately their ceiling of possible success
• Instead, they became duller, less motivated, and in some instances, paranoid
• And don't tell me marijuana isn't addictive.  It sure as hell is

Twenty years ago government kicked the living crap out of "big tobacco" due to health implications.  But now marijuana is OK?  What about the recent studies on the health risks associated with pot smoking?  What's really at play here?

Could it be that there are those in the government that don't want a voting populace firing on all cylinders?  That they're better served by constituents that have lost their ability to care too much?  That by providing distractions like pot, that folks won't notice or care about things like war, or the economy, or having a job, or the national debt, etc. etc.?

Maybe I'm the paranoid one. but I don't get this.  Not at all.