on one hand, I do agree. but on the other, what @LDoBe said.
add to that, it breaks the 4th wall. if you’ve ever seen a movie where the protag plays basketball, for example, and they show him shoot, then cut to the ball dropping thru the net; the casual observer might go along with it, but if you’ve ever played basketball, you immediately see how fake it is and then you’re out of the movie, no more suspension of disbelief.
similarly, anyone watching your idea who has ever done coke is going to immediately call bullshit. (depending on how it was shot, of course.) and that’s a lot of folks.
'cause a whole lot of folks have done coke.
not saying it’s right for a production to ask that of an actor, but an actor saying “I’m not going to do that” on the day of the shoot has a lot of veto power. firing him/her and having to re-shoot all the existing footage is prohibitively expensive and not usually going to happen, so I assume there is a pretty good give-and-take when it comes to the comfort level of the actors in these cases. I mean, if they’ve ever recreationally done coke, they’re probably fine with it. if I were to lay a wager, that’s the majority of actors simply because that’s the majority of adults that I personally know. maybe that’s the company I keep, but think about hollywood–I reckon my experience is conservative if anything.