Why? Dwarf Fortress only exists because it was given away for free for decades, bringing in tens of thousands of dollars in donations, and eventually leading to a fandom popular enough to bring others onboard with the project to produce a GUI and paid steam release version.
If something you build brings in a lot of critique, it is likely something of great value. Because something that doesn't have value won't bring much critique at all.
Their donation revenue was alright for a pretty significant chunk of that time. For the first decade it was ~$5k/month, which jumped up to ~$10k/month for the second decade before the Steam release.
Toady wasn't exactly raking in the cash, but he didn't need another job.
