It should not be part of the discussions but I think the various governmental units threaten to cut the services they think the voters most want and not the waste, duplicate or poorly performing services.
SS does have a problem as do most pension systems. The government made promises that it can not keep. These have to be fixed so senior benefits have to be part of the long term discussion, but they do not belong in todays debt talks. Paying the SS benefits will not increase the debt limit. The government can sell some of its "lock box" treasury bills (reducing government debt) to the Federal Reserve. The Federal Reserve will print new money to send to the SS beneficiaries. Of course this will be inflationary but then the government has being doing this for the past year or two to finance the recovery programs.