In this case, a massive part of the blame is of course with the US health care system, which basically makes it extremely difficult to survive old age unless you have a retirement plan and insurance - things that many self-employed developers never had.
The question I'd like to raise, however, is not "what is the root cause", but rather "what can we as a community do about it". Some trade professions take care of their elder members by forming a union and contributing to a common pension plan, but it seems that there aren't many unions for software engineers. We have the good fortune of being members of one of the best-paid professions in the world, and I find it very sad that we still end up with our members and elders falling through the cracks and struggling to survive.
[0]: https://www.gofundme.com/crunch-medical-fund/
[1]: https://www.theatlantic.com/technology/archive/2013/02/the-definitive-story-of-steve-wozniak-steve-jobs-and-phone-phreaking/273331/