Opiates allow me to conquer depression and major stress. Working at a company, with massive investment, several employees, and need to keep coding, keep morale up, lead a development team? Opiates turn what would be crushing stress and keep me positive so I can focus on getting stuff done. But could I tell our board about how I cope? Hell no.
There are many more folks in my position. Junkies give us opiate users a bad name, just like meth-heads make stimulant users look bad[2]. So, it's just not acceptable to mention usage, even when it's OK to say how "I'll really need a drink tonight" or even take smoke breaks during work. Which is funny, as opiates have very little heath side-effects (obviously overdose, but after that, constipation is the only real issue).
And yes, I've opted out several times. Once, like Paul Erdos, I decided to prove to someone that I could, and took a whole month off. Despite being on the equivalent of ~100-200mg of morphine a day, it was not very hard. (Sure, if you start IV'ing heroin, things might be different.) Overall, I decided I do better with opiates than without.
Any excuses that remove stigma and get society closer to rational discussion on drugs is an overall win.
1: Opiates are one thing that really work for depression. Mood stabilisers that all doctors want to prescribe leave me content to do nothing - literally. On them, staring at a wall all day is "just fine". Zombification.
2: Except most folks seem to think "meth" is some crazy other drug, not related to what they give hyperactive kids. No one seems to know meth is a legal prescription medication in the US. But then again, most folks don't know Heroin was a trademark of Bayer (name goes with Aspirin).