Developers are also the kind of people who will refuse to pay money for or use proprietary software on principle - regardless of price! I constantly see people on HN suggesting (often highly immature) open-source alternatives to free or reasonably-priced proprietary software for no other reason than the fact that it's open-source.

Just like being an author, it's hard to make a living writing (books : software) unless you're either very skilled+lucky (Brandon Sanderson : Jetbrains) or sell to companies (HR/marketing position at a company : either making B2B software or working for a software company yourself).