They held London, Liverpool, Newcastle, Middlesborough, Sheffield, Manchester, Birmingham, Coventry etc. Basically they held cities. Which gets distilled down to them being a 'London party' (or a metropolitan, liberal or 'Islington' one) by people who like to dismiss the working class populations of those cities because it gets in the way of their 'Hipsters and middle class students are all Labour have' narrative. In London especially it allows both the media/political class and their critics to keep indulging their wank fantasies of politics beginning and ending in Westminster because everyone else in the city is really like them. Except for the millions of precarious and low waged workers they walk past every day, who don't exist.