Why are the roads in such bad repair?

Yesterday I was out driving before my car died.  You can't help but notice all the road construction going on.  There was a sign in the road indicating that the construction was courtesy of some recent governmental stimulus program.  Ok, fine.  But answer me this:  Why were the roads in such bad repair to begin with?  Why are our bridges in such bad repair?  After all, federal, state, and local taxes have done nothing but increase over the years.  Aren't the funds supposed to be used for such purposes?  It is obvious that the money has been used for other purposes, but what?  Now that we are out of money, we can borrow money that we don't have from China so that our children and grandchildren will be stuck with the tab.  Somehow, I don't think this is going to end well!