Probably because the bidder is an aggregator sending the referral to many law firms, not just one. Individual law firms thus get outbid for an exclusive referral click, but can still pay the aggregator for a non-exclusive referral.

How does that work? The user is expecting to click a link and go to a page, not multiple pages. Or does the aggregator have an interstitial page? It sounds like a generally good idea but I don't understand how it works from the user's perspective.