Although you should obviously do maintenance, things will sometimes fail before they're officially due for replacement. It's not an exact science. So things should be designed to fail at least reasonably well. A failed water pump that takes the engine with it is a disgrace.
This reminds me of another bit of bad design: if you let the rear brake linings get too low on a Renault 5, the pistons pop out of the rear wheel cylinders and you lose the hydraulics. In fact since it's probably a diagonal split you lose _all_ the hydraulics when both rear wheels go.