Haven't they always been wests?
Only since 1987.
Wests and Balmain are foundation clubs - 1908. Back then 'western suburbs' were found around Ashfield.
Campbelltown were almost Newtown, or the New Campbelltown Jets to be precise.
By the 1980s, there were a lot of things going against Newtown. Financial and geographical.
And imo they would have survived longer if Kevin Humphreys wasn't forced to resign as the League boss. Newtown had a debt to the NSWRL (as I recall). At that point Newtown were ready to relocate to Campbelltown, the debt to the NSWRL was not being called in and there was every chance that the New(Campbell)town Jets would weather the hard times. I knew for a fact that the Campbelltown council was on board, the mayor had association with Newtown and lived in Campbelltown and was right behind it.
But Humphreys was ousted after that 4 Corners report (episode called, 'The Big League') and his place was taken by John Quayle (and Ken Arthurson). The debt was immediately called in and Newtown were forced to fold in 1983.
Wests were also forced to fold at the time (1983) but they took the League to court and won. Newtown were not so lucky. About 4 years later, Wests made the move to Campbelltown, keeping their Leagues Club in Ashfield. They essentially took Newtown's spot in the south-west.
Since then Balmain joined Wests in a joint venture and the JV also included a third entity, Wests Campbelltown. Although this year, Wests Campbelltown left the JV, leaving just Western Suburbs and Balmain... and Balmain are in dire financial jeopardy. If Balmain were to fold, the JV would also dissolve and I imagine the NRL license would switch entirely to Wests - the Western Suburbs Magpies could very well be the name of the team and they would most definitely be playing out of Campbelltown.
The irony is that Wests, the club that the NSWRL tried to boot out of the comp in 1983, are now one of the richest clubs in Sydney... thanks largely to their prosperous Leagues club in Ashfield.