Yep, exactly. it is a testament to it's design that they were able to last as long as they did, especially under the maintenance and use/abuse they received.

Industrial equipment in private practice i think is a little more understandable since profits are the concern. If it is down for mx for x hours a month causing y loss of production/profits and repair costs, but the replacement would be z hours down and e cost of replacement and installation cost, and z+e is greater than x+y than unless you can get a consideration of predictability, increased production through upgrade, reduced labor cost, or something else to tip the balance, you're always going to stick with the old equipment/part.

The military however has a greater imperative in the instantaneous full functioning use of a device/system/piece of equipment under adverse environmental conditions which demands a different metric. The problem is that those using the equipment aren't the same as those buying it and the military has no value for time. so even if it takes 14 hours to service and repair an aging pos for every hour of use, they just make their workforce work those long hours and get to retain the use without assuming any cost... until you look at retention... but they don't like that part because it means there might be a problem with them the people in charge.