it's just cheap nasty engineering, but bloody expensive when it goes wrong, which is what is so annoying. I had a Norton Rotary motorcycle with the chain fully enclosed and running in a bit of oil. Chain lasted forever, only needed adjusting with a new tyre, and when feeling guilty cos it hadn't been adjusted for about a year. Main thing enclosure did was keep dirt and water out so chain got easy life. Wouldn't be hard to do something similar on a car, though I would prefer it to be built into the engine itself and gear driven.