Why do people believe links are still a good signal? It is a textbook case of distorting a metric by relying on it. Traffic to (and engagement on) a site seems

Why do people believe links are still a good signal? It is a textbook case of distorting a metric by relying on it. Traffic to (and engagement on) a site seems to be a much better signal, for the many sites that use Google Analytics, at least. But not everyone uses GA though... Backpedalling now, PageRank is about weighted links. Link farms should have no weight to give, and links from the user generated parts of pages (which are easy to detect on most blog platforms) should be easy enough to weight fairly too. So it is hard to see why Googlebot gets fooled by any blackhat link techniques that Google humans are aware of, except maybe the case of selling links (influence peddling), but one can argue that is a social /legal issue, not a technical problem.