First click free is a multilayered Faustian bargain with the traditional print media. It preserves Google's ability to give their users what they want, which is searches which show high-quality, free information, like NYT or WSJ articles. It allows the NYT/WSJ/etc to remain on the only Internet which matters, which is the Internet you find at google.com.
Also, the not-so-subtle threat is that if you fail to implement first-click-free, perhaps because you believe your information is worth paying for, then Google will send navigational searches for your articles to scraper sites.
p.s: I thought this behavior was against Google's ToS...