Interchangeable cookie-cutter coder availability is Finance's number one priority. Definitely no room for critical pricers or infra written in languages that they can't frictionlessly slot someone else into as people leave. So python.
Also, arguably, Julia, while fantastic, just didn't do that much that Python didn't do already. It's main argument outside of tidier ergonomics was basically "speed without leaving Julia" but with Numpy and Pandas being essentially stdlib, that just wasn't a very powerful argument. Julia was basically too incremental to be worth switching to. It seems to have found its niche elsewhere though with the optimization people?