Why do girls' Yahoo Avatars always look so much prettier than the actual person they supposedly depict?

I have been constantly let down by seeing these cute young slim cartoon avatar girls only to see a real picture that is 90% worse. They are always either way too old and overweight or way too young. It takes so much time to actually get these girls to send me a pic and then they finally do and it is just letdown city. Is there a way to tell if a girl is really hot on here? It would save me a boatload of time. Thanks.