Re: What do people do on these OS's?
Hmm, I'd be a little careful with your statements if you "don't want to start a war" and you seem pretty set in your views for someone who who is "genuinely curious".
Still, I'll try to take you at your word :-)
What do I do with my Debian GNU/Linux box?
Good grief, many things including all the ones that you suggest have no "decent software."
Just because you don't recognise the name of a piece of software or it's not a supposed "industry standard" (what a loaded and misleading phrase) does not mean it is not "decent".
I record and edit audio and edit video using some very powerful and easy to use software.
I edit images using some very powerful and easy to use software.
I don't personally use "office suites" but I know people who do use Libre Office, including in businesses on systems I support.
I also do all that usual web browsing, email, IRC, messaging etc. I play just about any video or audio file (I haven't had one that doesn't play for years), I watch Youtube with free software (ie. Gnash and HTML 5 not Adobe Flash), I run servers for websites, I build run and maintain websites ... and more.
Actually, for what I do on networks, servers, version control, bits of scripting and code to do jobs, a tiling window manager, Emacs ... I could go on and on. When I see a non-modular non-free system like Windows or a another proprietary system like OSX, I really do wonder how I could do it all and am glad that I don't havbe to.
Most of all, GNU/Linux gives you a system that is truly discoverable. You can happily stay on the GUI (and many do), or you can start learning more about the system and setting it up to do what you want it to. There is nothing off limits, no "End User Licences" and secret software and codes. It is a free software (as in free speech) system that can be shared and adapted by everyone.