Why would any emoticons (even MSN emoticons, when they are for Messenger) be so excited about signs? They don't even have words. Although, if you already know the answer to this question you can click here to download these emoticons.
The smileys are so happy about these numbers because they're under the age category. And what's your age? Well - whatever your age is - it insinuates a party. It insinuates a celebration. Because it insinuates... your birthday.