The Americans and the French use a different notation for open intervals: The Americans use (x, y) while the French use ]x, y[. How did this notational divergence appear?
Notation $()$ is traditional, and $].[$ was introduced by Bourbaki.
Much of the Bourbaki notations and terminology became standard, but English speaking people are the most conservative ones in this respect:-) (Recall the history of the metric system:-)
Another example of the same is "injection", "surjection", "bijection". Many English authors still write "one-to-one", "onto" and "one-to-one and onto".
Another example: Bourbaki taught us that "positive" is $\geq 0$, and "strictly positive" is $>0$.
But many people still prefer "positive" to mean $>0$ and "non-negative" for $\geq0$.
Remark. I am educated in Ukraine in 1970-s, and I experienced a strong influence of Bourbaki on education. But I still like $(,)$, perhaps just for aesthetic reasons.