There was a time in the 1930s where weapons were simple and tactics yet to be developed where using ersatz tanks had a benefit. That situation is long gone. Tactics still play a part but mostly its getting people to become proficient handling the complex systems that they now have - from manoeuvring the tank to using the weapons control system to the communications systems etc. In short you need to learn on the actual kit you will fight (or something damn close to it) in order to become proficient. IMHO, that's doable even for reservists - vis the US ARNG - but certainly not the way we are.
Its equally problematic for ARes logistics trades who have no field serviceable equipment to train on and then have no opportunity to put their training to practical use in a simulated operational situation. At best a handful of them experience the operation of a static base NSE.