It just wasn't formalised prior to Vic Thorp's death in October 1941, upon which it was inaugurated as an annual award. Previously it may have been presented as a "best player" trophy, perhaps paid for by wealthy supporters who may not always have been flush in the Depression era, but certainly not as part of an annual gala event like the modern Jack Dyer Medal night. This was a time when Brownlow winners were informed of their success via telegram.Why would it not be awarded?
Richmond's first recognised b&f was presented in 1927. Collingwood's first was in 1927 and Carlton's in 1929.
Geelong stretches all the way back to the first VFL season in 1897, but there are a lot of gaps pior to 1930. Aside from Haydn Bunton in 1934-35, Fitzroy has no award recorded between 1929 and 1944, despite its players claiming five Brownlows in six years in the 1930s.