Why does Perrault give up sending reports to the Bishop of Pekin? (chapter 7)

Perrault gave up sending reports to the Bishop because he often failed to receive them. Perrault had no wish to continue endangering the lives of the messengers, so he stopped sending reports.

At intervals it was his custom to send reports to the Bishop of Pekin; but often they never reached him, and as it was to be presumed that the bearers had succumbed to the perils of the journey, Perrault grew more and more unwilling to hazard their lives, and after about the middle of the century he gave up the practice.