Did the filmmakers really intend for their films to have grain in them, or was it a feature forced upon them by the nature of their tools?
If non-grainy film stock had been available for the same price, do you think filmmakers would have intentionally picked the grainy film instead? Every single time?
To me it's less about what they wanted to achieve, and instead about what they actually achieved with what they had available.
As an over-the-top example: Most people (that I know) would agree with George Lucas re-edits of Star Wars with newer CGI are worse than the original edits. The only reason to choose the newer edits are because they're released in HD and the original is not.
If non-grainy film stock had been available for the same price, do you think filmmakers would have intentionally picked the grainy film instead? Every single time?