...with lots of implications...    It's a great example of a question that is (apparently) so common in our society that the answer may be given and everybody immediately knows what the question is...     Perhaps other implications are that the wearer has LOTS of friends who are girls, and thus may be a subtle way of boasting about the situation.     Or perhaps it's an example of a timid introvert who is so frustrated with his own inability to attract girls and others' repeated questions that he is merely trying to find a way out while saving face.  :}

Whatever the story behind the shirt, it was pretty funny to see.