Not to defend this, but there’s some time lag between the time a person dies and the time SSA becomes aware of it. So it’s inevitable that some payments are going to be sent to dead people for this reason alone.
Maybe in some cases but my father died on the 2nd day of the month and his SS check usually arrived on the 3rd day of the month. The Post Office in his town returned the envelope marked Deceased.
They may be required to do so if they are aware of a death.