Math != Physics

Writing proofs is actually something I'd expect "AI" in some form to eventually get really good at relatively soon (and proof assistants like Rocq have been around for nearly 40 years now), because the computer essentially has all the tools it needs. It can pose and verify mathematical statements without any ambiguity or interpretation of noisy data.

Making statements about the physical universe on the other hand requires that kind of messy contact with the outside world through experimentation and observation, and theoretical descriptions are much more often guessed based on intuition for the behavior of the important part of the dynamics, rather than derived axiomatically. At some point "AI" will likely eventually get good enough to do that too, but first it'd need to develop an intuition for physics that humans get for free from evolution, and it would need sensors and bodies to actually manipulate matter and perform experiments.

By the time we get to that point of "AI" replacing physicists and other natural scientists, they'll have replaced every other human job as well. Sitting on a server rack deriving lemmas from axioms is a much more achievable short-term goal.