Industry gets professional programmers by hiring people who have been hammering out shipping code in paying products for years, and years, doing support, maintenance, and new product development and research.
Grad students may be brilliant but that does not help give them any insight in to what makes a good ecosystem, toolchain, and feature set good.
We would love to have more professional programmers contribute: unfortunately those 1-based indices put them off.
More seriously: part of the problem does seem to be that Julia does have some significant differences from "traditional" languages (e.g. the concept of a "virtual method" is a bit fuzzy in Julia, what we call a JIT is probably better described as a JAOT, whether it has a "type system", homoiconicity, etc.).
That said, this JuliaCon I have met a lot more people from and classical "programmer" backgrounds. So hopefully that is changing.
I've seen quite an evolution over the past 3.4 years I've been using Julia and the 4 JuliaCon's I've attended so far.
Back at the 2015 JuliaCon, a number of us "older" professional programmers felt like we should stage a palace coup, because it did feel like the input of people who had "been around the block" a few times was not really valued. That's changed quite a lot (maybe because in the intervening years many of the core contributors have gotten their Ph.D.s and are having to live off their blood, sweat, and tears (plus lots of joy, to be sure) of producing things with Julia that people will actually pay money for). Yes, it was young and brash, but those awkward years seem to be past, and I feel the future of Julia is quite bright.
How was it with the origin and design with Python, NumPy, Matplotlib, Pandas? Were the people who originated these projects in their time any more professional and seasoned than Julia people are currently?
Where do you think most companies get "professional programmers" from, exactly?
Julia's been designed and implemented by some very bright people, and it shows.