Why can the position of the vice president be considered both very important and very unimportant?

Actually vice president always comes under the direct controll of president, hence it can be considerd very important because theres lot of critical responsibilities and follow ups which are carried on the shoulders, most of the times and then its very unimportant because in case of anybody any small mistakes or miscommunications then vice president will be directly responsible from the top levels to face the tough questions.