The problem is that the preferences of individuals does not match the preference of those people in a group.

A group (say, of castaways on a desert island) can easily afford to have 99% of people donate 1% of their output to support a 1% of their population that was paralyzed in the crash, and most would prefer not to watch that 1% die of neglect. But individually, no one can give 100% of their output to that 1%.

Left to their own devices and anonymous, people will slowly opt out of the voluntary contribution, and the situation will be worse than what everyone wanted. Unless the group has some means of compelling everyone to contribute.

I'd rather live in a society where everyone (including myself) was forced to contribute, than a society in which no one was. Living in a society in which everyone else happens to contribute to the things you'd like, while you don't have to contribute, is not an option that's on the table.

The key problem with referenda is they put an amount of control of the future into the hands of people who decide on important insurances based on which company gives the best cuddly toy, and give about as much complex thought to political decisions too (so are easily swayed by whoever sqwaks out their atrocious disingenuineness and out-right lies the loudest - not that I'm bitter at all...).

That would make it difficult for minorities and unpopular services. Nobody is going to want their taxes to pay the tax collector's salary, after all.

One of the many conundrums of modern politics is that the tax collectors could indeed collect more tax if they were better funded, so every tax dollar spent would recoup more than one tax dollar, yet this is resisted by the people who are presumably not currently paying what they should under current laws, and they've convinced people who do pay what they should under current laws, that this is a good thing.

I'd suspect there wouldn't be much funding to provide access to impaired people, either. Most people probably aren't all that interested in paying for things in Braille.

I live in an unincorporated township, with just a few residents. My road would never get plowed or maintained.

I didn't mean total replacement, in some cases it would work better, in other cases what we've got actually works pretty well. I meant some percentage of your tax should be controlled by the taxpayer directly, let's say 1% to start, increasing every 4 years by 1% up to, 20% for example.

I don't think 20% of the budget is capable of being discretionary. If you're really wanting to do so, some government agencies actually accept donations. When I sold my business, I donated to NASA. I couldn't earmark the donation for something like educational outreach as donations have to go into the general fund.

Related: a book Pratchett teased but didn't complete was about tax management: https://en.wikipedia.org/wiki/Raising_Taxes