So what happens to your simple encapsulated system when the diesel motor breaks down, or one of your hydraulic lines breaks? Does your simple encapsulated system them also say "we have no downtime, because we have a simple system"?
You leave port with 10 replacements for every component of the encapsulated device. Or just a full replacement for it.
Hidden complexity in the case of the diesel motor was made possible also because of know failure modes (how many years until the low hanging fruits all got solved, how many decades until the not so easy got too?) and standardization of its components (how many centuries just to understand and standardize the universal joint https://en.wikipedia.org/wiki/Universal_joint?).
