Utilities are public goods, and people pay proportional to the cost they impose on the system. And the economics work out well, not because there is a conscious effort to impose markets on people, but instead because incentives are aligned.
Postage works exactly the same way. No matter how expensive it is to get a package to you, you pay a fixed rate for it. However, you also pay proportional to the cost you impose on the system is that you pay per package.
Perhaps utilities were a bad choice of example on my part because of this usage confusion.
Actually, you do pay for untilities based on how expensive it is to get to you. The local power folks won't run a line to whereever you happen to be "for free". They'll charge you, the developer, someone. If you're a long way from "enough" capacity, the cost can be significant.
That's why some folks aren't on the untilities grid.