So, I'll play the devil's advocate in this thread and have personal experience in both the heavy party lifestyle as well as the very sober lifestyle...
For many the dependence of drugs and alcohol comes from some form of trauma, bad parenting. In recent psychology they are also finding a link between trauma and ADHD and as that area of medicine becomes more mature much of what used to be considered genetic is being considered to more frequently actually be a trauma response. As alcohol and drugs can help a person escape from that reality that they're living in it does provide them relief and can actually help them focus better and be more free and open minded. Of course, there are healthier ways to go about this than alcohol and drug addiction, but it's a truth that I think should probably be spoken of more.
This is very much happening first hand for me. I've been historically a casual drinker who didn't often turn down a drink, but also in the last 15 years I rarely had more than one or two at a time. However, I did end up having a drink or two every day probably for the last 25 years. I wouldn't turn down weed either and I was admittedly quite functional on both. After getting an autism diagnosis a few years ago and digging into some trauma in therapy I just kind of lost the interest in drinking and weed and haven't indulged in either in almost a year and a half. It wasn't ever a conscious decision, I just started to notice I slept better when I didn't drink and so I stopped. Quitting weed was actually harder because marijuana helped prevent me from having nightmares and really intense vivid dreams that were honestly so jarring that they'd leave me useless for an entire day. But life had gotten quite challenging for me for personal reasons through the pandemic and I wanted to be thinking straight through it all.
I don't trust big pharma anymore. I did in my 20's and was on meds for depression and while they sort of worked, I'd be lying if I didn't say they made me not be as wholesome a person as I truly am and would even use the word narcissist to describe areas of my behavior. In therapy ADHD was a big topic for me and my therapist even supported my use of cannabis as in recent studies it's been helpful for people suffering, but my memory retention of what I was studying was not up to my satisfaction so I've refrained from that indulgence. I'm hoping things balance out, but quite honestly when I listen to recordings of my playing live from 20 years ago when I would have a drink or two and some marijuana in me my playing was more inspired and more confident than it is today. It's a long process and I have faith it will all come back around again, but the shorter path is certainly just having some drinks and feeling better temporarily. This is the cycle and it's why people like Keith Moon, John Bonham, Kurt Cobain and so many others aren't with us any more, but also put out an impressive quality of work.
So, others have touched on the idea that "if you're playing better when under the influence you have other things going on," and I completely agree with that. But for some strange reason I felt like opening up a bit with my experience in the hope that it might shed some light on a rather taboo subject. So yes, I think it does actually help some people perform better, but it will probably shorten their life and come at an expense to their mental health over time.