When known delayed departure will badly impact on the remaining schedule, perhaps even requiring a crew change, fuelling time can be adjusted. During delayed departures, consider tankering fuel to reduce or eliminate refuelling time at airfields where faster turnarounds are know to be possible.
In addition to actual refuelling time, sometimes there can be a delay waiting for the refuelling equipment to arrive.
Even a small amount of avoidable turnaround time can have an adverse affect. Missing a departure slot could result in serious further delay. Then it will be too late to wish you had tankered.
Where company policy permits, intelligent refuelling could help pick up lost time. Even being 5 minutes early during previous sectors could make a difference when things go pear shaped at the end of the day.
Bean counters who think their business is money will not like avoidable tankering. Those who understand their business is efficiency will understand that time is a bankable item.