I think that, and genetics, can have a lot to do with it. My main golf buddy, and his wife, have no history of kidney stones. But their Son has them left and right! He drinks all kinds of energy drinks and iced teas every day. A long time ago I read an article that indicated that the epicenter of kidney stone affliction was in the southeastern and southern US! That's where the most iced tea is drunk in this country! Luckily, I am unaware of any history of kidney stone in my family, and never having one in 70 years of life, leaves me feeling pretty confident of never developing one.
Makes sense. Tea is high in oxalates and most stones are calcium oxalate, plus the warm climate offers the potential for dehydration.