Wow. This is amazing. I seem to be arriving... 19 months late to the party, but this is a topic that's been on my mind recently.
I agree, physical appearance is important. Certain details like height, weight, ethnicity and other distinguishing features will inevitably cause our characters to draw conclusions and opinions (often incorrectly) about other characters. Certain features are also telling about a character's personality - tattoos, hair style and color, piercings, artificial or natural tans, etc. It gives us the tiniest glimpse into their psyches, lifestyles and tastes. A character's appearance may be a reflection of their social status and background or it may reflect the image they want to project to the world - aloof hipster, put-together preppy co-ed, greasy slob, edgy biker guy.
Physical appearance, mannerisms and behavior build character and affect relationships. They're important aspects of character creation. And yet many writers (role players and published authors alike) include physical descriptions to ensure that we, their partners and audience, understand that their character is attractive, desirable, hot. That's right, folks. People should want to get with their character because she's got double D's, has long brown hair, and big bluish-greenish eyes (that change with her emotion, of course). She's not too tall or too short (she's just right).
Okay. So this author intends for her character to be perceived as attractive. Mary Sue qualities aside, attractiveness is not a bad trait. There's nothing wrong with wanting to have a beautiful character. But when the character's life and story do not influence her appearance or, conversely, when they are not influenced by her appearance, then what's the point of describing her at all? Just so we have a picture in our minds of who's talking? That's great (and necessary so we can envision the scene), but just saying that Character Z looks like X isn't enough. Let the story interact with her appearance. Show me how her looks reflect or affect her personality. Show me how the world treats her because or in spite of her appearance.
Physical traits should be reinforced throughout the story, little by little (I forget who mentioned this above, but I wholeheartedly agree). No info-dumping. Just remind us why it's important for us to know that Character X is attractive or tall or frail. Otherwise such descriptions - all the clothes she wears, the color of her eyes, the expanse of her derriere - are meaningless fluff. I've seen characters described as being "thin but curvy" or "curvy in all the right places," and I think to myself, "that's the writer talking." That's how this writer wants me to perceive her character. And I can't help but think this is some warped, sly version of god-modding, like I'm being forced to make my character think a certain way because of some deliberately vague wording in someone's character sheet: Be attracted to my character! She's hot according to cultural standards of beauty. Submit to her allure, plebeian!
*Ahem*
We want people to like our characters, and an easy (obvious) way to attempt gaining favor is through appearance. Hell-o! We all went to high school. We know what a popularity contest really is. So, granted, we think the more attractive our character is, perhaps the more popular she'll be. But think about this: who is your favorite character in fiction? Your favorite TV hero or literary villain? Why do we root for these characters or care about what happens to them? It's not because of how they look. Not entirely. It's because of who they are and what they do. It's because, as Minibit point out, of their personalities. Appearance without personality is just a picture. But when the two work in tandem, we're well on the way to creating a character.
That's my two cents.