This site is not about pre-issuance searches. See the others questions on the topic. It is only concerned with invalidating issued patents. You have a legitimate point, why give away a free search? Probably explains the utter dearth of responses to calls for prior art. Most appear to be nothing than so someone using google patent's prior art feature.
The concept that the site makes the examination process better means it has to deal with pre-issuance inventions. That takes away from work though for people who want to get paid to file bad applications.