I am curious.

Every time I depart at SFO, we have a departure delay due to cleaning

Also every time, the plane is sitting at a hard stand for hours idle and where the plane could have been cleaned.

I understand why we can't cater until the plane is at the gate, and why we why need to do inspection at that time, too. But why cleaning delayed for that, too? It seems an unnecessary delay for a terminal which is very busy.

Can those with knowledge fill me in?