It was an observation of the Founding Fathers (and one we've proven to be true, unfortunately) that government has a tendency to expand its own power. That's the entire reason the Constitution started out as a list of explicit things the federal government was allowed to do (and anything not in that list was verboten).
While a small government can't ensure that no one is ever in need (as a large government could), a small government also cannot take away your right to privacy, a fair trial or any other abridgments of freedom. The former is an acceptable sacrifice for the latter.
Jefferson said it best when he said "A government big enough to give you everything you need, is a government big enough to take away everything that you have...."