On pretty much every popular blog or news story that allows comments, there are links to soandso’s sex tapes. Why? Are the people who are adding the links somehow being paid to do it?
Sounds like link spamming to generate traffic. Traffic to websites can be profitable (ads, affiliate sales schemes, direct product sales…)
The people adding the links are quite possibly the proprietors of the linked site, or maybe aren’t people at all - it could be a bot.
Those are spam, probably pointing to porn sites. I imagine you can figure out the profit motive there.
Generally, they’re not people, but automated scripts (bots), whose creators either try to simply get a lot of clicks to their pages, or want to get you to download something harmful to your PC, and most of the time both and a couple of other shady things.