This is all true, but the reason people don't is the same reason as many human behavioural tendencies: (1) most people don't feel they have much money to spare

This is all true, but the reason people don't is the same reason as many human behavioural tendencies: (1) most people don't feel they have much money to spare (people on bigger salaries/incomes often get more expensive houses and cars so end up feeling like they have little cash available), and (2) people feel that "one dollar" is too little to make a difference to the dev's life so it's not worth giving anything. Whether those reasons are reasonable is separate; it's just the way most people act, and it's hard to imagine what will cause enough people to change that will make things better for developers. Better for developers to find ways of monetising via "pro" features, commercial support, etc, as it's easier for people/companies to justify paying money if they feel they're paying for a product or service.