alt Hacker NewsAs a bit of a shameless plug, I did some in the past[0] and am working sporadically on a "fork" of those[1] but it's a whole full-time work. There are hundreds of icons to do for apps alone. Each one needs to be done in 16x16, 22x22, 32x32, 64x64, 128x128 and 256x256 so if say you have 150 icons to do for apps, you actually will need to do 900 icons. And add to that that you'll need to cover categories, places, filetypes, actions...
Granted, you can do a 256x256 and scale it down to 128x128, for example, but if you care for quality some details will be lost anyway. So that's why nowadays you'll see most icon themes are just a bunch of logos plastered over a shaped background.
And what irked me the most was that a few weeks after that I released that first set via deviantart and opendesktop.org there were websites that included them in their sets and made them available for download in their websites, not even a redirect to my deviantart or opendesktop pages or something. And found out after that that some people were using them in commercial projects and stuff so I had to chase them asking to not use them since they were cc-by-nc'ed.
Never got a single cent of any of that. I love making icons, at some point I was even working for the icons that would eventually become the Breeze set for KDE5 with their VDG, but it happens that I also need money to buy the beans.