It all depends.

Fuel gauges rely on sensors determining the amount of gas in the tank. These sensors can be giving an inaccurate reading if the car is at any kind of position other than straight on the ground and not moving. Many fuel gauges actually are less accurate when full, as the sensor can be "below" the actual fuel level from excess gas in the tank.

Personally I notice that there's a significant dropoff after the gauge goes below the point between Full and 3/4.

Also, understand that the fuel pump works harder when the gasoline dips below the usual intended level of use, or the mounting point.

It's whatever the car engineer had in mind when they designed the car.