Why do I want traffic to my Facebook page? I can't make money there. I make money when traffic comes to MY site, not Zuckerberg's site. Yes, some FB traffic will click through to my site, but I'd rather spend my time and money promoting my own site.
This is only the case if you monetize with Adsense (or some other PPC or PPM advertising). If you actually sell stuff (or even if you are an affiliate marketer), you can make money directly on Facebook. It's an additional source of traffic and one people should not ignore.