Have a butchers at my China who thinks the seppos are less precise.
But none of that answered why in the absolute world a group would choose to initiate a rhyming slang for things such as the damn stairs. Rhyming slang is purposely obscuring.
It's insane to me, that cockney is half made up of purposely making communication more difficult or insular. Like, I get that there's complicated in group signalling incentives at play, but like, why?