I have a lot of Chinese customers all here for most of their adult life and they all speak "passable" English. They had to learn as most suppliers in manufacturing are Australian companies.
I have noticed with WL/ML that the FIFO girls don't bother trying maybe because they're only here to make as much money as possible in the shortest period of time, and as GFM has pointed out they don't really need to learn. I've found with some older girls who are here to get a PR (as well as earn the $$$) they actually make an effort.
Also our governments make everything easy for new arrivals so they don't have to make an effort. I know my ex books interpreters every time she needs to talk to a government agency and it's a free service provided by the taxpayers. She even had a court appointed interpreter during the divorce proceedings because English was her second language.