I believe many females see shy men as weak men. It can be cute to them at first, but in the long run, shyness represents a weakness in a man's character.
As a man, ask yourself this.. would you want a:
Skinny Girl - Fat Girl.
Non-smoker - smoker.
High self-esteem - low self-esteem.
Shyness is the opposite of confidence, which most girls prefer because its a position of strength in the ying and yang of the two. Girls may flatter shy guys with words to be nice, but at the end of the day, the reality is that they go home with the confident guys, and the shy guys go home sad and lonely.