Having someone other than the typical speaker on stage actually has enormous value. It's not true that there is an objective way to judge the value, even the technical value, of a presentation, particularly before it is given. So while saying "we want the best technical talks" sounds good, refusing to consider other factors actually works against minorities who -- no matter how blind and merit-based _your_ approval process may be -- often face innumerable other disadvantages in getting to where they are, including an overwhelming lack of role models in places like technical conferences.