If you are a risk-taker, willing to step outside the bounds of "normal" acceptable behaviour, then you are apt to try cigarettes, booze, grass, and harder drugs...........and grass is apt to be your first drug, simply because it is so available, thus it is seen as a "gateway".
Baloney. Drug use is a product of one's personality.
My first drug use was LSD, way back in the fall of '69. I don't think anyone would call LSD a "gateway" drug, but in my case you could claim it led to the use of a myriad of other pharmaceutical wonderfuls. (better living through chemistry)
I know lots of people that hold down jobs, have good marriages, and have smoked dope almost daily for 35 years. Is it good for them ? GOD NO!
But let's kick the nanny state the hell out of our business.