This is an aspect of human behavior. Sometimes people won’t do something if they aren’t forced to even if they think its a good idea. This is why the free rider problem exists. Your conclusion ignores facts surrounding human psychology. People don’t see a $1,000 donation to the government as being helpful if it’s just them doing it. They can see it being beneficial if millions of people do it. Hence an individual is unlikely to make a voluntary donation to the government whilst supporting increased taxation for everyone in their income bracket.