Glass plates were still in use in the 50's & 60's. Looking in 1930's publications all the manufacturers offered a wide range of plates while film tended to be mainly limited to smaller sizes.

It's probably the invention of Safety film and the wide scale adoption of the International darkslides that heralded the switch from plates to film. If you look at early negative the nitrate film is not as sturdy as modern film base and would not have been suitable for larger sizes.

Ian