Sounds like you watched a bad movie.

Burns' Vietnam series is currently being shown on SBS on Saturday night, JaSin.

Problem with your views is of course they are a lot mixed up and incorrect.

The NLF (called incorrectly and derogatorily by the US the "Vietcong") did smoke cigarettes.  If you had watched last night's episode you'd have seen them smoking.

The PAVN (Peoples' Army of Vietnam) (called incorrectly the NVA) also smoked.

Everybody basically smoked in those days.  Even the Australians.  However where we were different was that we only smoked in Defended Localities (ie "firebases" or Nui Dat or Vung Tau), not out in the field on operations.  Cigarettes give away someones position by their smell, as well as their butts.  Indeed, I've seen old diggers still remove the tobacco from their butts and spread it around, rather than just throw a butt on the ground.

Burns' doco series is good but it focuses primarily on the Americans.  Funny that, hey?  Seems they forgot that the ROK, Australia, New Zealand and Thailand contributed land forces to the struggle against Communism in South Vietnam.  The West Germans sent a hospital unit (something not widely known), while for the North, Cuba, Czechoslovakia, the PRC and Russia all sent forces.  None of them went South though.  They all remained in the North as advisors.

I have Ken Burns' playlist of the Vietnam War on my youtube account. It is such a shame that I have to listen to playlists of movie critiques instead.

This was an awesome book, author of Black Hawk Down.

https://www.amazon.com/Hue-1968-Turning-American-Vietnam/dp/0802127002