1. People who make profit and don't want to lose it to the FOSS crowd 2. People who are ashamed of their code 3. It's status symbol and they 4. They don't realize open source exists 5. They're a corporation which reuses hardware/software/IP from their commercial line of gear (such as D-STAR, Yaesu System Fusion, etc)
N1MM logger [0] fits 3.) - it's the most popular contest logger, it's totally free, absolutely packed with features, and worked on by volunteers, but it's closed source because Tom (N1MM) doesn't want to lose control, but it really seems he enjoys the limelight.
WB8ELK fits into 1.) with regards to his round-the-world high altitude balloon tracker packages [1] He sells his kit for $150, with a BOM cost of $20 and no more than 1000 SLOC. I spoke to him and all he had to say was "he has no plans of open sourcing." I assume it's because it's a good income.
I'm not sure where the WebSDR fits in, but I feel like there's a good reason.
It really confuses me, given both the FCC rules about keeping the airwaves open and unobfuscated, as well as amateur radio being exclusively a community of hobbyists.
There are exceptions of course... The MD-380 firmware, FreeDV, and GNU Radio all being some good examples of open source projects. But it's far from universal, and less common than I'd expect.