Because earlier there were "Actual and real" First Class coaches, 2 coaches of Non Ac Cabins/Sleepers berths and 1 with EC type 2x2 recliner seats also Non AC . But as these were made in aroound 1990-1995 these coaches were removed after 25 years and were replaced by normal General class coaches under the name "Vice First Class" So Vice as in, "Its not first class but assume it as first class"
All 3 FC coaches were and currently are Non reserved and MST only