There were many reasons for Hitler to not attack Switzerland, as the country did not have any natural resources which could have attracted Hitler. Another simple reason is that Hitler never felt the need to invade Switzerland as the whole point of attack could be to utilize the train lines, supply lines and other facilities to ease up the transportation of German army with which Switzerland never messed even during the war, German armies were passing through Switzerland freely, the famous stories are common about sealed rail cars passing through Italy to Germany. Switzerland played an almost neutral role during war which could also be a reason for their safe grounds.
Though Hitler had a plan to attack Switzerland called “Operation Tannenbaum”, which was cancelled later.
