In the lo-co life has changed, almost all STBY days end up as work
The business model caused crewing levels to be at minimum and rosters all to max/min FTL's. Thus any disruption today caused a change in tomorrow. SBY's were not called out at departure time, but used in advance due to crews being out of rest hours for their next duty. SBY's were firefighters due to bad rostering practices and NOT for last minute disruption scenarios, which was their basic concept.