I was going to say that you can combat this by simply linking to your website from all these profiles but it turns out that virtually all social media sites `rel="nofollow"` homepage links. Which in itself is a pretty sleazy tactic (sure, the official reason is to combat spam).
Before they did that there was tremendous abuse by spammers. I'm sure the reason they haven't come up with a good workaround for regular ppl is more in line with their general sleazyness
