Why Default?

Why is there talk of default?  It's like Obama is trying to create one...  The math is simple:

$250 billion in monthly revenue 
-$22 billion in monthly interest on current debt
-$76 Billion in mandatory spending (S.S., Medicare, etc...)
-$75 Billion/mo in Defense 
=$42 Billion available for "other discretionary" spending

Why would our president allow a "Default" (or even talk about one) given the math?  Could it be that he benefits politically from the "crisis mentality"?  

Yet somehow we (i.e., the U.S. taxpayers) currently borrow $105.83 BILLION dollars per month to run the federal government.  Where does that money go? 

Let's See:

Source: Missing Money