The reversal adds to the power of what you
mean by stating the same idea negatively and then positively, or sometimes
vice versa. The negative to positive is stronger because it sets up an
expectation.
Medical expenditures used to be small, not because
doctors were cheap or hospitals were well managed but because there
was only so much medicine had to offer, no matter how much you were
willing to spend.
Two competing causes, and the writer
tells you which is not the real one and which is, starting
with the negative. Imagine the order reversed—and
the loss of suspense.
The trouble is not with the facts. The trouble is
that clear and honest inferences have not been drawn from the facts.
It's not so much that Wallace thinks about politics
all the time as that she is continually registering its consequences
on the lives of all the people she knows.
It is not that problems are not solved and questions
not answered, but every solved problem generates dozens of new ones
and the process gives no sign of ending.