Because collecting only one type of taxes would cause massive economic distortion and would inevitably burden people unequally. Different taxes have different properties. Some hit certain groups harder than others. Some hit certain types of businesses harder than others. Far better to have a whole series of modest taxes than one form of ruinous taxation. Do some countries not have property taxes? Yes, but they're small tax havens that aren't really a good model for the vast majority of nations.

But as far as optimization, consider some examples.

Property taxes also work best at the local level because the spending needs of municipalities don't swing heavily with economic conditions. The federal government has spending needs that vary wildly with the economic cycle. During a recession, the federal government needs to massively ramp up its spending. But at a local level, a recession doesn't mean you suddenly need twice the number of firefighters. Property taxes are pretty steady over time, so they're a good match for the needs of local government. The federal government's income tax revenue goes down during a recession, but that's ultimately fine, as the federal government controls the currency. They can afford to sustain massive deficits during bad years and make it up with surpluses in the good years. (Well, if the federal government was functioning as designed.)

Income taxes also make more sense for government entities whose jurisdictions are difficult to avoid. If you fund your city entirely with income tax and no property taxes, you may find your community completely overrun by retirees who want services like anyone else, but don't actually earn much taxable income to pay for them. If you fund your city entirely through a large sales tax, people can just drive and shop outside of city limits. It's much harder for people to avoid federal income tax simply by moving house. Unless you're leaving the country entirely, you're not avoiding the reach of federal income taxes. (And sometimes even that doesn't cut it!)

But property taxes? The only way to avoid those is to not live in the city at all. Which, from the city's perspective, is fine. If you don't live in the city, then you're not putting much burden on the city's infrastructure and services. But if you want to live in the city and enjoy all the benefits that come with living in a city, you have to pay the city's property taxes.

In short, different taxes have different properties, different benefits and drawbacks. Funding a society through a diverse arrangement of taxes allows much more efficient optimization of these taxes. It's a much more intelligent system than just trying to fund it all with one big dumb tax of a single type. That's more the way of Medieval head taxes, not modern nation states. We used to have simple tax systems. We stopped using them because we realized there were better ways to do it.

Most modern nations have higher taxes especially on the rich