But you are right, from a design stand point, they are very flawed.
To be fair, miners are running the cards way above what they were ever designed for. 99% of people buying those cards maybe play a game an few hours a day, which isn't as hard on the VRMs as mining LTC.
Mining LTC on a GPU is like driving your car up a very steep hill at maximum revs constantly for 24 hours. It'll do it for a certain amount of time, then the engine will pop.
When I bought my 7970 GHz edition almost a year ago, it was $450! It was one of the best video cards you could buy at the time. I've also been careful to give it good airflow, watch the temps, and clean it regularly.
In you're car analogy, this isn't just your mom's Toyota Camry running up hill 24/7. This is a Nascar Toyota Camry. See the difference? It should be able to handle the load.