a public good is a good that is both non-excludable
and non-rivalrous in that individuals cannot be
effectively excluded from use and where use by one
individual does not reduce availability to others
It's hard to imagine a society not oriented around roads, since the government has been building them for so long. But lots of people have an economic interest in using and maintaining the roads.
> An even more obvious example is something like pollution control.
Ah, the good old, "Libertarians can't handle externalities."
Well there is lots of free-market scholarship on pollution and courts going back decades. If you're actually curious about it, I can point you in that direction. If you've already made up your mind, then there's no point elaborating.
One quick aside: during the Industrial Revolution, government courts sided with industry in pollution matters, granting them the right (sometimes monopoly) to pollute. Plaintiffs were ignored by the government in pollution cases, since industrial progress was more important than their health. So government actually made pollution worse...
The normal response by anti-tax people is that all of the roles of government should be funded by opt-in systems, where you agree to pay a fee to get the service.
However, this doesn't work for a lot of public goods that suffer from free loader problems; you can't prevent people from benefiting from the good if they don't pay. Take, for example, roads; either roads are public, and a freeloader can choose not to pay and use them anyway, or they are private toll roads, and a person could be literally imprisoned because every road to move around requires payment to use.
An even more obvious example is something like pollution control. Society has an interest in preventing people from dumping toxic waste into rivers and lakes, so we create restrictions. However, someone has to enforce those restrictions, and that requires funding. Without taxes, we would have to volunteer to pay money for the enforcement; however, why would I pay? I get to enjoy the clean water whether I pay or not, so why not just freeload? This will mean enforcement funding will not be there, and people can just pollute as much as you want.
You need a way to get everyone to contribute for public goods, which is why we need taxes.