That's an interesting point, to be fair. Do you actually think that this is actively pushed by the tennis authorities though, or simply a result of peer pressure amongst the players themselves?
I think it is a bit of everything. It's in our culture, looks often out weigh talent in music, films, and it's working its way into sport. With more and more female sports stars getting involved in FHM-type photo spreads, becoming more like celebrities followed when they go out, featured in fashion sections of red carpet events. This culture of pretty = worthwhile feeds into all areas of life, the audience, the competitors, the authorities, the sponsors, the TV companies that pay the authorities for broadcast rights, and I think to a large degree it is subconscious, so ingrained in us that we don't even realise it is affecting our decisions as to who we watch or when or whatever.