She explained , `` Harry HAD to be an orphan - so that he 's a free agent , with no fear of letting down his parents , disappointing them â Hogwarts HAS to be a boarding school - half the important stuff happens at night ! She explained in a 1999 interview with The Guardian : `` Harry had to be an orphan â '' so that he 's a free agent , with no fear of letting down his parents , disappointing them ... Hogwarts has to be a boarding school â '' half the important stuff happens at night !