The ideas of this article are inspired by a claim that the Soviet Union Kirovets K-700 tractor was developed to be a missile transport vehicle, but was mostly used as a heavy duty tool in agriculture.
Vehicles that are gathered to a military base form a easily destroyable high value target. Rockets can always penetrate enemy territory and the locations of military bases can be obtained in a multitude of ways. If the vehicles are in civilian use, then their location changes periodically, just like the location of nuclear missile submarines changes, and the vehicles are dispersed to a wider area. In civilian use at least some of the vehicles are readily available exactly in a region, where they are needed at the start of the conflict.
Shelf life issues are diminished. The equipment is being tested continuously. The equipment will have a considerable wear, but after some time it has to be replaced with new equipment anyway, because military equipment does become technologically obsolete.
If the equipment is rented out or used for providing civilian services by the military, then the rent and service revenue can compensate the maintenance and replacement cost of the equipment and training cost of the military personnel that operates the equipment. All of the funds that would have otherwise been spent on acquiring new equipment, replacing the old equipment, can be spent on research and development of new equipment. Given that the sales value of technologically obsolete equipment is less than the price of new equipment, the model, where equipment is held in a base till it becomes obsolete and then sold, produces financial losses.
If the army personnel parks the tanks, armoured vehicles, mortars, etc. to the neighbourhood, where they live, e.g. take a ride home after a hard day of work, then the local population gets used to the equipment of the local army and is able to distinguish the friendly military vehicles from foreign ones during a conflict. For the sake of semi-anonymity they should not park the vehicles right next to the house, where they live, but it's OK to park them somewhere in the neighbourhood, e.g. somewhere in 300m radius from home.