Squawk-7600: I wish more people would make your point and not allow themselves to be brainwashed by the "beancounter" approach. Revenue is as important to a company as costs. When you consider the average fares charged, even by the LoCos, it is obvious that a few pence/cents on the ticket would more than cover the marginal costs of the extra fuel carried to give crews more flexibility.
Unfortunately the current attitude by airline managers towards what is a "suitable fuel" to be carried simply pushes the safety margins in terms of time available to crews whenever anything goes array. Quite frankly, the supposed savings are rather nebulous when you consider a) fuel gauging errors b) fuel loaded by the bowser to the nearest 100kg c) assumed pax/cargo weights d) arbitrary diversion routings.
It appalls me to think that there are crews around who think that they are doing a good commercial job by flying round on marginal fuel loads whilst the commercial departments of the airline refuse to charge realistic fares!! The idea that 50p/£1 on a ticket might be a deterrent to travelling by air is not borne out by the spend per head of those same pax when they are onboard or in the shop before flight.
As a grizzled old F/E said to me once - "the fuel tanks are for fuel, old boy, not for air!"