Not that many GIMP users, you mean.
You know that print media includes things like flyers, posters, etc. right? Promotional materials?
If you get out and walk around a while in (at least in areas with a population density greater than north dakota) you may notice a lot of them. Those were pretty much all created using CYMK.
I say may, because if you stay fixated on your phone while walking the entire time then you probably won't notice them, but please do me a favor and look up from time to time - I'm getting tired of almost hitting people walking across 4 lane divided highways. Even when you honk they don't look up from their phone.