[wildmusings]

This, and it allows the negotiating countries to save face when they make compromises. All real diplomacy is done in private for this reason.

[pluma]

By the time elected representatives get to vote on the deal, the decision boils down to "completely reject it" or "accept it as-is and hope that maybe some of the concerns will be noticed and adjustments will be made". And considering how politics work there's a huge incentive not to make the entire deal fail that far into the process.

[wildmusings]

In the US, that's the intended design. The President negotiates treaties and the Senate ratifies them in an up or down vote.