Messenger knows as well as we do that the risk to us is very great. You needn't agree to anything you are unsure of...
The fact is the only reason anyone will likely agree is because there have been warnings shown to us by previous generations of blanks and by Surgeon, saying that the South Block is where everyone goes to disappear... There have been... some signs of this. Teams now are rarely full teams of six as they were in the East block.
In Messenger's understanding, our options are either to keep playing the games in hopes of leaving soon enough to avoid being taken by the earth, or else work towards everyone's escape, with the potential of things ending disastrously more quickly...