Worpdress networks that allow users to create blogs (either free of paid) . Noobs and dirt bags seek them out to spam them relentlessly for backlinks because they don't know how to do real SEO honestly. It's actually a waste of time because if the webmaster is any good, the links never stay, or they spam a site so bad that it just shuts down. Either way, it's a shitty way to get temporary links that don't do you any good anyway. Garbage links from random unrelated sites just proves to Google that you have a garbage website. But, everyone has an excuse or an old 1995 article that tells them differently, so people keep repeating old tactics and and spend more time spamming the web with garbage, than just doing the work.