Because they have spent a lot of time analyzing the one's that are actually BRECCIA pipes.
Briscoe went in there many years back and staked everything he could find that was available. They have spent considerable time and effort mapping out 431 BRECCIA PIPES out of the 1777 claims they did.
Why continue to pay out money for the other claims.
The claims were made so they could do the analysis.
The analysis is in, they kept the Breccia pipes and let the rest go.