Programmers from all over the world work on their free time on projects, some foundations exist supported by individual donations and companies' funding. Some companies release their code as F/LOSS.
There is no single entity that dictates what software is built and moreover people working on F/LOSS are (I would say) on average more aware/sensitive of their work's impact. I know for example that GNOME people are actively trying to better accessibility and would welcome the help (your time and skill or donations, or both).