That's not accurate. The fuel gauge is still there (battery percentage). What they took out was to see how many miles you have until empty. I think the car metaphor is both accurate and inaccurate to this. Everyone knows that the MPG that is provided is generally the maximum you can expect. On a MacBook Pro, you can expect up to 10 hours. That means you're likely going to get less.
What you don't see in cars is extreme performance requirements like you would in a computer. For instance, if you are running a process, the processor is going to spin up and try to take care of that task as quickly as possible. Then when it's done, you basically go back to not doing much at all. It would be like driving by flooring the vehicle, going as fast as it will allow for two minutes and then coasting the rest of the way. Each app and task is like a different sized hill and you don't know what's coming. So if you end up flooring the accelerator a lot, your battery life depletes. But you if you ACTUALLY using the computer like a car on the highway, you're going to get much better mileage.
The issue is in how you are using the laptop. If you're not stressing the processor and driving on flat ground in overdrive (so to speak) you'll get 9-10 hours. If you're encoding video, playing games, compiling code, working in Photoshop or hitting the GPU... you're going to suck up battery much faster.