A better system would be to have a very accurate reading of the power left in the battery.
This isn't technically possible. Batteries are chemical devices, storing a chemical potential that when called upon, converts a chemical reaction into the current we need.
So there's no quantity of electricity sitting in the battery that can be measured electrically.
Long ago with lead acid batteries that needed topping up we could measure the specific gravity of the acid electrolyte with a hydrometer to get a very rough chemical indication of the charge contained. Nothing like that is possible with our lithium batteries.
All we can do for greater accuracy is have a device to measure the charge being withdrawn as it's used so we roughly know after the next full charge what we can expect to get out.
Meanwhile the meters we have just measure the decline in voltage as content is used to get an indication of what's left, not very accurate.
.