How exactly are you going to decide what to load for 1 person? 2 people? 50 people? How much of each item do you need to ensure that everyone gets exactly what they want to drink in the correct quantities? And then, where are you going to put it all? Valentines Day flight to Prague, 50 people booked each way... One bottle each? Two? Three? 300 bottles of champagne for a return flight! What are you going to take away from the bar to fit that in? The gin? Red wine? Bitter lemon? How exactly would you do it baring in mind you have to do it for EVERY flight individually, taking into consideration the day of the week/time of day/weekend/holiday/composition of pax/number of children/weather...... Suddenly having a standard bar loading looks pretty sensible.

You'd need an army of people to decide what to load, not too mention an army of people counting every item in the bar to get the correct amount, taking things out of "over catered" bars, rather than simply filling every bar up to a known standard.

Are those logistics complicated enough?