This has been a very reasoned group of responses to a serious question and it's spurred talk about other choices singers/actors make, including the effects alcohol, which is more widely used, I would guess.
As a former long-term smoker, I would like to offer some opinions on some of the recurring comments in this thread:
“It’s none of our business” – actually it is, if we are non-judgemental about it. We learn from other’s experiences and knowing that a singer is or was also a smoker explains vocal changes and that can benefit budding singers and the choices they make early in life.
“Smoking can ‘improve’ your voice” – sort of like athletes taking occasional steroids to improve a different type of physical performance, smoking comes with the same caveat – this activity can be dangerous in the long run.
Personally, I think smoking is more likely to initially diminish a singer's lung capacity before it alters vocal quality.
Thus far, we've named the following smokers - with a ? behind those we're uncertain about.
Julie Andrews
Michael Ball
Tammy Blanchard
Laura Benanti
Eileen Brennan
Kerry Butler ?
Norbert Leo Butz ?
Liza Chain
Kristin Chenoweth ?
Daisy Egan
Jarrod Emick
Michelle Federer
Leah Hocking
Patti Lupone ?
Tyler Maynard
Euan Morton
Adam Pascal
Billy Porter
Ann Reinking
Daphne Rubin-Vega ?
Colm Wilkensen
I agree that it is difficult to imagine a broadway singer jeopardizing their 'instrument' by smoking, but because of this thread, maybe we can begin to understand the 'why' of it.
Wisdom often comes with age, but sometimes age comes alone
