From my recent time on the 767 flying the MEL-SYD-BNE triangle, the normal fuel load was around 10T.
To carry an extra Tonne of fuel cost between 30-40Kg of extra fuel burn over the sector. Seems like cheap insurance to me.
Quite why dispatch calculated the fuel to the kilo, sometimes as low as 9T, based on the fact that the weather was forecast to be 100' above the alternate minima never ceased to amaze me. A classic case of measuring with a micrometer and cutting with an axe.
Obviously very few took flight planned fuel. With such a short sector length, and such a minuscule cost to carry, why would you?