lederhosen
I would argue that fuel and noise pollution are not considerations while we are in a pandemic.
Indeed, EASA released SIB 2020-02R5 which refers to recommended covid procedures, and our (very cost sensitive) management informed the line pilots that airports have agreed APU can be used despite any environmental restrictions while the SIB is in force. This is in order to provide ventilation and water pressure for hand washing.
The travel industry is already a major target for government restrictions, and we don’t need skippers failing to supply plenty of ventilation for passengers when engines are off.