If citizens were allowd to allocate 100% of their tax burden as they see fit, you would find out quickly what services the state offered really mattered to people, and what "services" are just vote buying and handing out money and favors to the connected.
If taxation was voluntary, and the individual was able to allocate 100% of their tax burden as they see fit, then you would be approaching a moral system of social and financial interaction.
Another added benefit would be that the citizen has to be sold on the value of any given service, rather than being forced to pay for things whether they like it or not, or whether it violates their moral code or not (for example, War).
It falls apart pretty fast, once you put a little thought into it.
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Many services can't/don't/shouldn't target who they benefit.
For example, supposing when cops pull over and arrest a drunk driver, everyone who drives in the same area benefits - the sensible people who volunteered to pay for it and the freeloaders/idiots/drunk driving fans who didn't.
When your town builds a flood preventing drainage system, everybody in the area benefits - people who paid and people who didn't.
When armed forced prevent invasion/bombing of your country and your favorite oil-supplying nation, everybody benefits - people who paid and people who didn't.
So where's the incentive to contribute? Just kick back and let some other suckers shoulder the load.
Until eventually the suckers get tired of being played, and enough of them quit, too, and then whole thing collapses, because there aren't enough people to keep it going any more.
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And that doesn't even address what happens when you get people choosing diametrically opposed goals. Or choosing goals that the vast majority find utterly vile.
For example, suppose some people put up 5M for the purposes bombing country X and overthrowing its leader, while some people put up 5M for supporting country X's leadership against the rebels. Now what? You do both? Or just let the team with the most money win? Just openly and directly make "money buys policy" the procedure?
What happens when some people put up 1M earmarked for building statues in town squares with plaques depicting hooded KKK members hanging black people and longing for the days of white superiority?
Or maybe a grown man sodomizing a young boy and a plaque describing the beauty of




philia and how it needs to be legalized and accepted?
Those going to go up under your plan? Because the money's been raised, and letting individuals be themselves and fund whatever they value is going to create this great "moral system".