@559
(1) because fixmystreet is way more convenient, e.g. mobile phone app so you can report from the street; the council website reporting often didn't work for me even from the office computer.
(2) Fixmystreet is a convenient public record so you can send the link to twitter, councillors and others if the council doesn't act. And you can post a link here to warn others. The council system is less transparent.