Often airline managements will obligate the crews to use the OPTIMUM configuration output, because they fall for the word OPTIMUM.
EMIT, while you clearly understand a bit of the background with the laptop, you're a little 'off' on that response. That's not the reason why some companies choose to recommend the OPTIMUM setting for FLAP at all on Airbus FBW.
Many Airbus operators know the background for OPTIMUM (as you correctly say it's the flap setting that allows the theoretical max weight to be lifted off the runway...)
BUT they are NOT necessarily 'falling' for anything by choosing OPTIMUM as a standard procedure.
No. The simple reason is this; if OPTIMUM were NOT used by the crew, it leaves the process open to pilots making a large number of laptop calculations... fiddling with various flap settings (1/2/3) while they 'explore the envelope' to see what the max flex is. That's probably NOT a good idea. Why?
Because MORE laptop calculations for a single takeoff, means a GREATER chance of a MISTAKE
Using OPTIMUM CUTS DOWN the number of calculations... and makes it clear to crew they are not supposed to run calculations at various flap settings to find the max flex.
Considering the minimum financial gains from using a flex value a degree or two greater... clearly running more than one calculation to maximize flex is really a waste of time. Particularly when unnecessary calculations can add significantly to the risk.
Some airlines might be better off using TOGA everywhere... (when even one event costs millions of dollars and (mis)use of flex is often a factor).
Although this is not likely a practical solution in management's eyes, because that airline may be ridiculed in the industry, TOGA everywhere might still be safer. Considering the number of events which would have successful takeoffs, instead of running into the grass at the end of the runway (before finally getting airborne).
Worth thinking about.