I personally know a few ML professors at my university who are not taking any CS grads as pHDs. They only want people with maths degrees.

A lot of these CS professors are themselves maths grads.

CS is discrete maths, which is not quite the same as statistics.

People have been doing statistics for decades, which is mostly all that machine learning is. Coming up with a fancy new buzz word for stuff that has been for decades, doesn't make something "elite".

You know, statistics is a branch of mathematics, and mathematical education itself can be considered "elite", if for no other reason then for the irrational fear it induces in most of people.

Most of high school graduates decides to pursue more "practical" topics like CS, leaving mathematics to those chosen few who dared to study it :)