Because it's easier to scale hustle then relative humidity. and high relative humidity and high precipitation rate are the associates. I should know because I grew up in both greater New Orleans, which is subtropical, and the Oklahoma panhandle, which is semi-arid 5% relative humidity or higher is normal in New Orleans. While 6% relative humidity is relatively familiar in the Oklahoma and Texas panhandles.
The reason for language diversion is the isolation of the people who speak the same language, but due to diversion and lesser contact between these people, now the language is used only in the dialects.
