Niche as in for every one systems programmer there are dozens of people writing API Glue.
By hours of work spent and lines of code produced the latter is in a whole different scale than systems programmers (which is a very badly designed term anyway).
I have a much more close relation with other niches than with web programming, even if web programming is part of my core skill set. I mostly interact with a few sites daily, even though I spend some time there. But I spend a lot of time with software like xterm, emacs, calibre, cmus,... and more with tooling like make, bash. While I'm not working on those, I had to become quite familiar with their working to troubleshoot some bug. Emacs is more important to me than AWS and GitHub.
