Right, but the presentation of the singer in popular music is much different that in musical theatre, where the creative teams (director, playwrights, composers, choreographers, etc.) are much more a part of the popular discussion, akin to cinema. They both can be lauded or criticized by individual performances by the musicans/actors/etc, but theatre (in most cases, I feel) is much less centralized around a single participating artist that pop music. I guess, to sort of simplify my point, my opinion is that pop artists have songs written for them, but in theatre the singers/performers are hired to portray the songs already written.
Did I say it wasn't? I meant the differences in the expectations between the two different types of performers by the general public is different because of differences in their mediums.