it _Have_ to be the modders descision, perhaps someone have created that works well because it can't auto repair.
Perhaps not the point is if im creating a game/mod/whatever, i dont want the engine telling me "you can't do that". Seriously, Many of us wouldnt be here if the engine did that, Most of us are here because the engine let us design and create the units we want, By forcing such a artificial we are limiting what modders can do, if you don't like a mod/game have auto repair play one of the many other mods there are, That's how it is, there are many games where i think "if only that unit dind't have that ability". But in overall i enjoy the game because it is balanced around it. Because thats how the developers designed the game.