Could you explain why you elected to depart from the short runway knowing that the longer was available?
Yes, very easily. The performance calculation that we performed showed that we were able to depart safely from the shorter runway; if it hadn't, we wouldn't have attempted to depart from it.
I'm really not sure what point you're trying to make.
Sure, we can 'fit' the numbers to the runways but at the end of the day, experience should lead a crew to make a decision to select the runway that poses the least risk to the operation.
Nobody is fitting the numbers to runways. Again, we will only depart from a runway if the performance calculation shows it to be safe to do so. To give an example: In Barcelona, departures are from 25L with a TORA of around 2600m. 25R is available for "performance reasons" with a TORA of around 3300m. Taking your simplistic approach, we should always request 25R for departure, because it is the "least risk" option, even though the performance software shows that we can perfectly safely depart from 25L. Never mind the huge delays that would be incurred by requesting the non-standard runway for departure; it is "less risk" and therefore it would be poor airmanship to accept the shorter runway! I think that you're ignoring commercial realities.
In the end, Fuel left in the bowser and runway behind you is of no use to you.
As
Penko has already said, part of the job of a captain is to operate efficiently, while still maintaining adequate safety margins. I could fill the wings and put the trip in the centre on all sectors I operate, demand the longest runway and take off with TOGA thrust on every departure, but that's not what the company is paying me to do. Therefore, I make sensible fuel decisions taking all relevant factors into account, and use the software provided to optimised performance.