Yes I do completely fill my gas tank when I get gasoline because I hate running out of gas and always want gasoline in the tank.
I usually go to the gas station after my gas tank reaches 1/2 tank or I'm near a gas station and my gas gauge drops a little ways near the half tank mark.
Keeping the tank full means I don't have to worry about running out of gas or having enough gasoline to get to the gas station.
That way I know if in an emergency and I need to go somewhere that my gas tank is always full of gasoline and I can just get into my vehicle and take off.
Some people only can fill their gas tanks halfway or just a little bit to get them from point A to point b as they live paycheck to paycheck and have to wait until they get some more money.