^Yup. I don't have a camera so all my photos come from other people. I don't know how its like for you guys, but when I go out with a group of girls at least one is snapping pictures all night and by the next night they are on facebook.
I have just a few old pictures of myself on facebook so people who add me know who I am as I can't be bothered to upload new ones. I'm tagged on maybe a few.
I don't think I ever had a picture with any of my girlfriends online. A few of my girlfriends uploaded pictures of me with captions that screamed "he's mine bitches, gtfo" so yes, to me uploading pictures of your girlfriend in 99% is because you're insecure. Being tagged on a picture with your partner is a different story though.