This has become a little more common lately, but probably still not as common as it should be.
Part of the problem is funding. You can get 3-4 grad students or ~2 postdocs for the price of a developer. Plus there are lots of existing mechanisms for funding them: training grants, internal and external fellowships, working as a TA, etc. A developer would have to get paid out of research funding, which is already pretty limited. The National Cancer Institute had a program for staff scientists, and the Chan-Zuckerberg Initiative just launched one targeting microscopy, but there aren’t tons of options, especially not for open-ended roles.
There’s been some adverse selection too. I briefly had a programmer but it rapidly became obvious he was working for an academic salary because no one else in their right m8ns would pay him more. I ended up rewriting all of that code, and despite this, my boss keeps sending me fresh-faced undergrads “to do the coding.” I guess the idea that you get what you pay for hasn’t sunk in yet. That said, we’ve also had a few that were excellent and were interested in the projects; I think they were both hired as part of some complicated arrangement where their spouses were recruited for more traditional academic roles.
Another part of it is that code quality hasn’t been a huge priority. That is finally starting to change, but most labs have a lot of code that was unceremoniously promoted from “one-off prototype” to “critical infrastructure” without too many changes. (This, incidentally, gives the lie to peoples’ obsession with YAGNI).
Finally, if anyone does need a neuro/ML themed developer, I call dibs :-) Seriously though, I completely agree that we have have more specialized roles (dev, technical writer/editor) and I think that whatever place manages to make this work could become a research powerhouse. Some of the bigger institutes (the Broad, Janlia Farms, etc) do have some jobs like this already.