Anyone who has owned a car has ultimately dealt with failure of a sensor (parking), or A/C failure, battery shutdown or a tyre puncture. Part breakdowns like these are pretty common, at least relatively.
In a car however, the most stress (mechanical and thermal) is faced by the engine and engine-parts. If you think about it a little more, you could see that the most stress is faced by the piston-rod and connecting shaft. Those and related parts face constant tensions and compressions, on the order of many times a second, and not to mention the higher temperatures.
Despite that, I rarely hear of such failures (in proportion to other common failures mentioned above). What could be the reason for this? Are those engine parts over-engineering to never fail (almost, 'cause nothing is certain), over the lifetime of the vehicle?