The only reason I don't use it is because I use windows. While you can theoretically use it on windows, nobody does.
What do you use instead?
I think a lot of people use make on Windows. I've had several jobs with a Windows dev environment, and they've all used make. My current dev env is cmake on Windows, so I don't touch the makefiles, but it's still using make on Windows.
There aren't that many options for cross-platform projects. A lot of people use cygwin or the Windows Subsystem for Linux with make and/or cmake native.
I also go directly to make on either cygwin or unix for one-off builds all the time, in non-C/C++ projects. make is super handy for resizing images or running a batch of tests on a program generating graphs. Anything where you need to generate files that only update when another file is touched is a good job for make.
make -j is extra handy on windows for some situations since it's hard to get gnu parallel to run in cygwin and the parallel perf wasn't very good last time I checked.
I use Make for everything from frontend builds (don't like grunt/gulp) to rust apps. The better I get at Make, the more I love it.