Perhaps they meant to avoid problems at immigration at the destination country. By law visitors to a foreign country must have a return or onward ticket as proof of intention to leave the country afterwards. Sometimes they surprise you and ask for it. Just the beginning of this month I was transiting at BOS, international to international, CBP asked to see my connecting ticket. So I was about to show my boarding pass on my cell phone as I had checked in online before and got seat assignment immediately. She made a fuss about not switching on electronic devices so I had to talk my way out of it including showing my airline and airport ID badges