I think you should be able to make AND delete them from within the defenses tab rather than swapping to the facilities, selecting them from silo, then delete.
But a mechanism where someone might not know there is something more efficient can be good. Then some players are smart and recycle. Others delete. This creates more variation in the game and lets someone thrifty or resourceful catch ahead in a small way and is rewarded while others waste. This can be a good thing to add to the game. This helps separate the good from the ugly and creates more variation to the game and more to do and learn. Making it more complex but also potentially more fluent and intuitive! In other words, reward the good and punish the bad!