"The market" not attractive enough - there's nowhere to put your money other than "the market" (including bonds, commodities, real estate etc.) unless you keep it in currency, and that's even more susceptible to government takings.
Is there a limit you see in taxes?
Do you have investments yourself? Maybe you donated all of your investments to the government after realizing how little you were being taxed?
Your last question is silly. The reason why I can simultaneously support higher taxes, yet not voluntarily donate money to the government, is because advocacy of higher taxes can raise far more money for government than my personal donations. Raising money to fund government is a collective action problem; if government relied on donations to run, it would fail because of freeloaders - in essence, a tragedy of the commons. But by collectively enforcing mandatory taxes we can make government work.
It's arguable whether giving government more money results in government working better.
By some accounts government is a demonstration of waist and an exercise in excess.
Government departments are always chronically underfunded, primarily because no government department PR employee ever got promoted by saying "we have enough money".
We are _nowhere_ near that point. And no one is saying tax capital gains at 100%; but I've never seen a convincing argument that it shouldn't be at _least_ the same as income tax.
https://taxfoundation.org/why-capital-gains-are-taxed-lower-...
That article goes out of its way to paint a picture of someone purchasing stock in a C corp with money earned from earned income and then eventually sold.
And yes, the corporation would pay a corporate tax rate (although almost certainly south of 30%), and then when that stock is sold, there is likely a 15% hit on the gains.
It is an unconvincing argument though; since salaries from a c corp are taxed too; if previous taxation was a deal breaker c corps wouldn't exist at all.
It is also unconvincing since capital gains are only taxed at the time of realization, it is an entirely different mechanism. As taxes goes, I can't choose to hold off paying taxes on income for a decade and invest that money; essentially compounding that money. But that is exactly how long-held unrealized capital gains work.
And insult to injury -- the entire idea of 'carried interest' is a give away to hedge funders. Even if you kept a low capital gains rate, carried interest as a concept should just be removed from the tax code.
Certainly it's not easy getting outsize returns reliably, but the idea that the return is earned in a way that scales with the amount invested sounds very dubious to me.