It's just a matter of how much they want to invest in what.
In many cases toll roads mean that the government didn't want to/wasn't able to invest in building a road, so they let a private for-profit company do it for "free" (meaning without tax money) and that company then recoups their investment using toll.
Some times toll roads are used to steer traffic. Some cities for example have a city toll that's meant to discourage commuters from using their car to get into the city and instead get them to use public transport.
The first case means the country doesn't raise enough tax, wastes too much tax money or has other priorities than road infrastructure.
The second case is totally valid since it uses tax to discourage unwanted behaviour.
That's what happens if you don't have public health care.
A small insurer or even an uninsured person cannot bargain with large pharma companies. If they try to, the pharma company will just not sell the product, because it's more expensive for them to lower the prices for everyone compared to losing one small customer.
But if your whole country's health system bargains at once, it can get much better deals, because not taking a deal means for the pharma company that they'll lose access to millions of potential customers.
That's why for example in Europe Insulin costs about 10% per dose compared to what people in the USA have to pay.