Pure narcisstic reasons, I guess.

You have control over what you want to show and don't in your profile pic. In a pic, unlike in reality, you can choose how to present yourself, possibly how you want others to perceive you----pretty, smart, cool etc.

I don't upload a pic of my face on the internet for everyone to see, because of security reasons. I'm neither a public figure nor a celebrity, and I hope to keep it that way.

Maybe things would be different if I were a teacher or something on this site for business opportunities. In that case, perhaps there might be the merit of showing my face since a personal pic would more connect with students.

How do we change our profile picture?

1) I don't like to change my dp  because I like people to recognize myself quickly. I think I'll change only if I feel that picture is not representing me any more.

2) I want to show myself  as I really am.

3) I, personally, like a simple photo of the person and don't like cartoons characters, animals and so on, but of course I accept them as part of another personality.

@ Rummy: Of course, my handsome personality.. lol... well, I have the same dp since May-2009 and never though of changing it as yet..!!

By the way, your dp is unique even in this post ;) I am interested to see how do you change it..!!

well i think the picture is something that allows other people to see you as a person. if the person doesn't have one, it doesn't mean he is "empty" lol, but still you won't find him as interesting as the other ones. you might as well can make an opinion about that person about his picture.