I manage (and share with my peers!) the books for an organization with GNUCash.
I collaborate on and write papers with LaTeX, write my code in languages with open standards, use primarily open source compilers, and run my code on Linux cluster which use open-standard parallel communication APIs and open-source implementations.
I do not play video games.
My office printer is plug and play with Linux/CUPS.
All done on my trusty custom linux distro (Exherbo) for years. Oh, and I haven't reinstalled since 2010 but I am running the most recent open-source GNU/Linux software.
Maybe my life and my needs don't match others', but then again maybe erikbye's don't either. Anyway, that is why I do not care about more people using Linux. If anything, more Linux users have made the internet a less useful resource for helpful Linux knowledge.
Why should I care?
P.S. my phone is another story, but I expect different things in that space.
And you probably shouldn't care, except for altruistic reasons :)
Linux has 1950+ games on GOG and 6500+ on Steam. Some of them AAA.
When it comes to file formats, I'm sure there are certain formats that poses a problem, but at least not the most commonly file formats exchanged. Like Microsoft Office formats; LibreOffice opens pptx, ppt, xls, xlsx, docx, doc, docm, etc.
Inkscape as mentioned above, opens Adobe illustrator files.
Both GIMP and Krita opens Photoshop files. Krita perhaps being the most appealing alternative to Photoshop users (UI-wise).
And normally, if you have clients, they don't arbitrarily send you arbitrary files in random formats. You have agreed on a workflow and file type.
Well, you should care. You should care when your clients or friends send you a file in a format that you can't open or transform properly on Linux. When you want to print something and your printer doesn't have drivers for it. When you want to play an AAA game and it's not available for Linux. Etc., etc.