Case in point, a regionally successful classic rock band my son plays for recently fired their lead singer for showing up to practice and shows drunk/stoned. Musicians may drink, but the vast majority take their craft very seriously.
I knew a guy who worked as a graphic artist. But his company had a “zero tolerance” policy–because it looked good to their clients. He had a part-time band & sometimes they smoked a bit at practice; they rarely gigged. Unfortunately, there was a surprise drug test one day.
So they fired him. They hated doing it–they liked him & his work was good. Testing for pot shows recent use–days after the smoker has come down. And he wasn’t exactly a surgeon, pilot or bus driver. Still, he lost his job.
And good for carrying flasks.
Not to hide the alcohol, of course. Just to carry it hands-free.
Ski lift operator
Just yesterday, I was volunteering at the library bookstore, and we got a bunch of copies of “Beer Advocate Magazine”, which none of us had ever heard of! 
I ran the truck repair shop for a large company for 13 years. I got to know all the top brass because we also serviced their vehicles. They would all stop back at the garage for a drink in my office. It got to the point where I was drinking all day. I never got falling down drunk but at times I would catch myself slurring my words. I basically had a green light to drink at work all day. I quit drinking about 5 years after I left there.
As a veteran of bar bands I can attest that Arrendajo is correct. A musician who gets drunk at a gig quickly gains a bad rep - and rightfully so. I’ve had had the displeasure to play a 4 hour gig with a guitar player who drank continually. By halfway through the second hour he was convinced he was the next Eric Clapton, but sounded horrible. We covered for him as best we could and never played with him again. The sad thing was he was pretty decent when sober, but had no self confidence and thought he played better when drunk.
Hedonistic lifestyle? Not that it doesn’t exist, but most of us put on a party face while performing, then went home to our wives after the gig to resume our “Ordinary Average Guy” lives until next week.
I wasn’t trying to say it was allowed, just that you could get away with it pretty easy.
My info comes from celebrity level musicians, I would assume things are different on that level in the sense that people are less likely to say no to you and you have more handlers to compensate for whatever mistakes you make.
I suspect some of these examples were not so much where as when. The 80’s were just different.
I love Margaret Cho, but I would probably never pay to see her live again after she showed up totally blitzed and wandered into incoherent babbling for half her show. He opening act at the time figured what was up immediately and stayed on stage trying to improvise working her state into something she was “doing” but it only partially worked.
On the musician thing. I’ve helped a friend set up the stage for many blues, rock, folk, and cow-punk bands. Other than the cowpunk guys, who pounded PBRs nonstop, there was hardly ever more than a single beer being sipped. Weed, on the other hand, burned like there was a fire sale going on.
Good times.
Not on countries where it’s legal. In Australia legal brothels will have a zero tolerance policy for drug use amongst their staff while at work. They’d tolerate a small amount of drinking but not to the point where it was noticeable to the clients.
Good way to fuck up the count and/or get jacked. Don’t get high on your own supply, dude.
Like most jobs, there are a lot of myths surrounding musicians. But the thing is, playing music is hard. It takes thousands of hours of practice to get good enough to play in front of people, and going on with your mind chemically altered is not a recipe for a good performance.
Regardless of their lifestyles off stage—hedonistic or not—a musician that goes on fucked up is not likely to give a good performance. And if they fail to give good performances, no one is going to pay them to do their job.
Hell, the Rolling Stones fired Brian Jones in 1969 for showing up messed up to practices, recording sessions, and shows. However hedonistic you might think rockers are—even big stars, even in the freaking '60s—they have to be able to play.
Unless you play punk rock. 
At most of the tech or consulting firms I’ve worked for, drinking was a fairly big part of the work culture. Regular office happy hours, drunken holiday parties, late night after hour parties, drinks with clients, beer in the office. Needless to say, I know for a fact that many people showed up to work drunk or hungover from the night before or simply “worked from home” because they were in no shape to come into the office.
There were still “rules” though:
-Don’t act like an asshole (particularly to partners or other important people)
-You still need to get your work done and not fuck up
-Don’t show up to work the next day LOOKING drunk or hungover (i.e. one analyst I had to send out to buy a new shirt because he obviously threw up on the one he was wearing the night before and slept in the office bathroom).
-A director getting wasted with his boss at a strip club at 4am is ok. A kid from the mailroom blazing up a joint in front of the partners in a bar will get fired.
Being a known cocaine and/or amphetamine user, in and of itself, won’t necessarily get you fired from an investment bank/brokerage as long as you aren’t blatantly obvious about it. What matters is the effect it has on your job performance which, based on my observations, can be positive in the short run but very negative in the long run.
Quiet Riot singer Kevin DuBrow used to consume the contents of a bottle of Jack Daniels at his shows. It was also common knowledge that the bottle contained tea, which made it a little less outrageous once that got out.
Unfortunately, that wasn’t his only vice, and he was believed to have been dead for at least 6 days before anyone noticed. 
Entrepreneur? Up until your business goes bankrupt at least.