Interestingly, the extent to which the simulators, for lack of a better word, "simulate" reality is unknown- in some cases, being killed in the simulation results in the person being killed in real life. It is possible this is only an extreme case, (as it is a fail safe in Vault 112, and a method of unlocking an armory in the VSS Facility.) Since, as previously stated, these simulators are known to have no civilian or entertainment applications, the question remains whether they were part of a previous training simulation or other project, possibly involving the development of power armor. Again, due to the limited information available since the bombs fell, this may never be known.
Known VR simulators
There are at least five known sites with VR simulators - Vault-Tec's Tranquility Lane simulation in Vault 112 (run by Stanislaus Braun as part of the Vault Experiment), Virtual Strategic Solutions, Inc.'s Anchorage Reclamation simulation in the VSS Facility (now known as the Outcast Outpost), the Flight Simulators at Nellis Air Force Base, the VR simulators in the Brotherhood of Steel Hidden Valley bunker and the broken VR room in the X-13 research facility at Big MT.
The simulator at the VSS Facility is labeled "SIM-U-TEC Chamber 003", suggesting that at least 2 more simulators were built by VSS Inc. Whether these were functional is unknown. It is possible that there are simulator rooms behind the doors; you see them when you go down with the elevator.
Nellis Air Force Base near Las Vegas used Virtual Reality simulators to train pilots. After the Boomers settled there they began to use the simulators for the same purpose, hoping to one day recover and refurbish a bomber and put the training to use.