Would you like to see how private industry would handle city water system, and how much subscriptions would cost? They probably could do it cheaper, but they would charge the hell out of the end consumer as profit. Because thats the idea of private industry - profit.
Not saying private do everything but if they already are and it's cheaper why screw with it?
Charging a consumer or taxing them, what's the difference
Take the bridge analogy. Why screw with the ferry business and build a bridge?