I see why you might say this, but it's is not the case in my situation. I'm an introvert and have been turned off of psychs. Plus, (and I know this may be specific to me) plenty of people I know that are into psychs are pretty outgoing people. Also, I've thought that it's possible that introverts could use stimulants as a way to combat their shy nature. For instance if an introvert suffers from anxiety, they may use amphetamines as social lubrication.
Just a thought, these things vary from person to person.
But generally speaking, I would agree that extroverts tend to gravitate toward stimulants. But I would think that introverts would generally have more of an affinity for opiates. And I'd say that both intro/extroverts can take to alcohol.
I'm an INTP/ISTP and amphetamines are my drug of choice. They make me feel confident instead of pointless and insecure (dx with generalized anxiety, dysthymia, and schizoid personality disorder), and they cause me to actually be interested in the people, events, and conversations around me. Like, I talk to people about things out of a genuine interest, not from a place of disinterest and disconnection.
I feel like amphetamines jack me into the vividness of life, the actual experience of the thing, whereas at my baseline, despite the fact that I fake engagement and appropriate affect constantly and so well so that no one is involved with the real me but me, that vividness is like a frequency on a radio whose antennas are never able to pick up more than a stream of noise that I observe but do not experience.
Being sober of drugs leaves me standing alone, an object placed in a life it can't feel, surrounded by experiences that don't engage her and people I can't ever seem to remember details about. I'm just all smiles and encouragement and helpfulness, all joking around and sarcastic, smirking asides. I'm reliable, unusually competent, and pleasant. Trustworthy and independent. I'm stressed/anxious and a workaholic and endlessly friendly. I'm that person externally because pretending to be someone who is engaged and who people see practicing her values daily through unflagging and quiet helpfulness/support, a commitment to producing high quality work, and an ability to problem solve, take advantage of opportunities, and put into effect solutions designed to benefit myself and others, might lead me to something close to being that person on some level some day... even if not really, on another level I can kinda, mostly, secretly believe that relentless hypocrisy will eventually become the truth. Or anyway, if not, at least I am painting a lovely fiction to cover up the empty space beneath.
If I think of how I am off the drugs, I see myself as a figure standing inertly in a school corridor while life bustles around her. I am registering the activity on a delay, muffled, blunted, curtained, always of the scene and never in it, jostled on occasion but too far removed to understand or react. But I continue moving my sober ass through the static and down the chaos of the hallway, lockers and faces a blur as I walk, because that's the only thing to do as a functional member of society.
But drugs... drugs make life real to me. The signal to noise ratio improves. I feel real. I care to chat. I'll solve your problems and feel mildly pleased when you love my solution. I'll feel connected to people in a way that isn't built upon the constant, irrational fear that someone will see the real me and call me on it. I can speak with her and enjoy it and just have it be a pleasant moment in time that alights over me and lingers, the warmth of friendly approval from someone I respect a lingering breeze. I can care enough to make plans with people.
It's not just stims, though I'll take stims over most anything else, it's that drugs in general alter my spirit enough to actually be able to watch a show and be too absorbed to do anything other than laugh and enjoy myself (weed), kiss someone and feel compelled to take it further with levity and pleased sense of fun (MDMA), explore the relaxation you can feel in a softer world, freed from life as a sensitive animal AND, bonus, eventually sleep deeply and wake up missing chunks of time that passed before you went to bed (Xanax).
My point is to affirm your argument that an individual addict's drugs of abuse don't necessarily follow from that person's observable traits. A genuinely bouncy, active, extroverted happy person won't necessarily love MDMA the most because it matches her personality the most closely. Ditto with a thoughtful, introverted thinker type and hallucinogens. A normally chilled out, relaxed, unflappable, unstressed type won't necessarily fall in love with pills that deliver the similar experience.
Drugs of choice are more complicated and intimate than that. Our preferences develop based largely, though not solely, on what drug can give us what it is that we are looking for through the use of drugs.
I think if you ask yourself why you are an addict, really, you can come see why you might prefer one substance over another. Some addicts are eager to detach and live in a softer world. Some addicts will take anything to feel something strong and real and indisputable. Some addicts want to enjoy themselves. Some addicts want to forget and be purged of the burdens of identity, memories, and realities of life. Some addicts want to eat more and laugh harder at The Simpsons. Some addicts want to broaden their minds. Some addicts want to die.
I think the problem with addicts is that we've crossed that line separating the option to use from the need to use. As we become addicts, we spend more and more time coping with life this way. And we live as though a life without our drugs would be an unfortunate, undesirable situation, maybe we hurt ourselves more deeply than we realize. I take pills to experience a better world and avoid my baseline reality, my baseline self. So multiple times a day, I am insisting to myself that I need this pill because without it life is less worth living.