Brand management was the sole domain of ad agencies. Years ago, when one wants to make a brand known they turn to the professional spinsters of print, audio and video. I think the world has changed a bit for the better.
Because the world of marketing has evolved, and today the companies that supply marketing communications and brand strategy are very different. The Ad agencies should do what it says on their tin – be agents for the creation of advertising, and accept that the strategy work that feeds their creativity will be devised elsewhere and without their involvement. Since branding has become more central to the success of most major clients, it has moved further away from the core competencies of advertising agencies.