Source: The Toronto Daily News, May 6, 1915
Given the attitudes, health concerns, and advertising restrictions regarding tobacco products, Toronto newspaper readers won't be seeing appeals to send smokes to Canada's overseas forces in their morning read anytime soon—a general appeal for morale boosting/easy to barter items would be more likely.
The soldier depicted in this ad was created by cartoonist Bert Thomas for a similar campaign across the Atlantic for the Weekly Dispatch newspaper in November 1914. The image of a Cockney "Tommy" telling Kaiser Wilhelm II that he needs a smoke break helped raise approximately ₤250,000 in donations from the British public. "Arf a mo' Kaiser!" became a catchphrase whose use appears to have lasted in the U.K. through World War II, when it underwent a slight alteration to reflect that conflict's German leadership.

Elsewhere in the Ist-a-Verse
Do people in the armed forces even smoke that much anymore?
I'm pretty sure the smoking levels hasn't gone down too drastically,if at all, its just that mass media has stopped advertising smoking for some time now. Kids, or any demographic really, can't see interviews of soldiers smoking because they view them as heroes, which make them more likely to pick up the habit.