IIRC, most of those pushed over the side were to make room for other incoming evac choppers.
When Saigon was falling in 1975 and the US Embassy was being evacuated, dozens of South Vietnamese helicopter pilots loaded their families and friends on board their helicopters and flew out to the couple of US air craft carriers that were off the coast to escape the North Vietnamese Army. It is pictures of those Republic of South Vietnam helicopters being pushed over the side of the carriers to make room for other incoming helicopters to land. The South Vietnamese pilots had no desire to return to Vietnam and become prisoners of war and ‘re-educated’ as communists.