“No, the analogy is a good one because mobile bandwidth is a shared resource.”
But that is not why water and electricity are metered. Those are metered because it actually costs money to provide each unit consumed, and this is in addition to the money it costs them to deliver each unit even after the infrastructure is in place. Internet providers only have the infrastructure fixed costs and they don’t increase with the volume of data moving over it. The carriers are not paying for every gig of data moved over their backbones, and they are not actually producing the content so there is no unit cost.
The effort to cap usage is just a way to slow growth so the existing infrastructure will last longer while they make more money back on their capital investment. A flat rate would pay for the water and electric distribution infrastructure because they have fixed initial costs and fixed maintenance costs — just as wireless infrastructure does — the difference is that each unit of water actually costs the provider money to purchase and deliver while gigabytes of data cost the carrier nothing.
Bandwidth is no different from water or electricity as far as infrastructure build and maintenance costs go. The real difference is in the demand curves. You probably don't need 10x the amount of water or electricity currently being delivered to your house, but you'd certainly be able to use 10x (or more) of the bandwidth.
If you think "gigabytes of data cost the carrier nothing" then feel free to open your own ISP and price your services that way and see how well you do.