Why periodic work is uniquely hard to verify
Routine service is checked continuously by everybody who uses the premises. If bins are not emptied, somebody notices within a day. Periodic work is different: nobody watches high dusting happen, the result is not obviously distinguishable from the week before, and the interval is long enough that memory is unreliable. Those three factors together make it the easiest part of a service to let slip.
It also slips without anybody intending it. A task deferred once for a legitimate reason, then again because the first deferral was forgotten, becomes a task that has not happened for eighteen months. Nobody decided that, and nobody noticed until the condition of a surface made it obvious. A record is the only thing that interrupts that sequence.
