For Google, the more a website is popular and important the more it should rank in the search results. So if a website has a lot of backlinks and good quality backlinks, it will rank high because many people are "voting" for it. But if the backlinks are contained in social profiles or forum profiles in the field which says "YOUR WEBSITE", It's evident for Google that these backlinks have been created by the owner of the website himself. In other words it's the owner of the website that is "voting" for his own website in multiple profiles and Google knows that. Please can someone with more SEO experience explain why it should help the rankings anyway?