First. Because the government serves more than just you. So your priorities don’t always align with the needs of the entire populace. There are lots of things that need to be funded, but you don’t even know about.

Second, you can to a certain degree. Most charitable contributions are tax deductable. Meaning you can lower your tax burden by selectively funding what you want.

You vote for that by choosing the political team with the spending policy that best represents you. But it’s a bundle and not spending decisions a la carte.

Some disaster relief charities used to let people decide how their donations would be spent. Donors overwhelmingly voted for rebuilding houses, because everybody needs a house, and replacing someone’s house is nice and feels good.

The charities ended up with way too much money earmarked for housing, which they were legally required to spend on new houses. That excess money could have been spent on boring things like sewage, but they were legally barred from doing so. The result was a lot of people with unnecessarily big, fancy homes with no working toilets or running water.

The charities quickly dropped this practice, because donors directed the money to what felt right instead of to where it was actually needed or would do the most good. And that’s why we don’t run the country that way.

You’re asking for direct democracy.

I wouldn’t want to have to take time to review budget proposals for my municipality, province, and country every day after I get off work. We have people for that.

It’s expensive to have elections.

You can also not choose where your money goes to. If I choose all my money goes to schools, am I still allowed to use the road? How about choosing everything except street lights and promising to not go out after sunset?

Pick the politician that says they will fight for the proirities you prefer the most. They may not get their way but there are other people in the (country/region/town) with other preferences than you and you still get to use the roads, schools, streetlamps and whatnot.

Let me ask you this.

What do you know about building roads? Running schools? Setting up a lab to do cancer research? Keeping a navy afloat?

In a word: no. That’s not how a representative democracy works.

Name a public service you cannot live without. I’m going to say the ambulance service. So when I crash my Ferrari into a concrete pillar, they take me to the hospital and I survive. It would be a shame if the service had been closed due to a lack of funding. All because a group of entitled, predominantly male libertarians had run a campaign to withhold tax money for this supposedly useless service based on the fact that they never needed an ambulance in their life.

You voted for someone to represent you. That person then hires a team of people to assist them in making decisions about complicated things, such as the education system, the transportation system, sewage system, finances for all of those plus a hundred other things that no one person on the planet can know at once.

Then that person makes a decision in they believe to be in your best interest.

If you don’t agree with that person’s decisions then you can cast a vote for somebody else to replace them.

You can choose where your money is spent: it’s called elections.

For instance, vote for orange pedophiles and your money is siphoned off and given to billionaires, Gestapo-like paramilitaries, middle-east forever-wars, fuck-flights and Barbie advertisements for the DHS Secy, and personal jet-setting for the FBI Director.

Most bonds or tax increases I vote on say what they are for, and the money has to be spent that way. I can’t decide the specifics, but I can vote yes or no on road maintenance, or school funding, or whatever.