Say you have a database, and need pull data, do some heavy math computation, then present this data in a pdf report with a QR code, pulling images and processing them in the report.
In Python, it is without bells and whistles: psycopg2, numpy/pandas, reportlab and may be use PIL. Wanna stick this on S3? boto3.
In Julia, it's all very fragmented. LibPQ is immature, DataFrames.jl is nice, ??? (what pdf conversion tool?), images.jl (300 stars), qr code generator?
The problem is not the speed with most tasks. The problem is availability of tools. I am sure that will come with it, but why not just use Python at that point? I am not a fan of Julia and that's nothing to do with its features. It has immature ecosystem, with terrible IDE support (Atom/Juno raises my blood pressure), debugging is painful if non existent, error messages are all over the place, everything falls apart as the immature dependencies change and error messages don't help at all.
Julia is fun in your jupyter notebook. If you try to build apps in production environment in my team, expect push back if not straight up refusal to initiate such a project in the first place.
Syntax was amazing around 0.4v and it went downhill from there.
I am sure someone is going to nitpick my comment and provide a way to do it in Julia, but that's missing the point. The point is Python is miles ahead of what it does. In production systems, robustness + maturity matters.
Also, don't forget ancillary aspects of a programming language. When we put a python repo together, I am rewarded by an endless supply of developers that I can hire and immediately work on it. With Julia, the supply of engineers is limited and it is such a pain to train people to use it, learn its quirks, spend nights and weekends fighting with it and the business doesn't give a fuck about it.