Over the past 50 years the reliability of cars has improved a lot, the reliability of bikes has not. And according to Globalti on this thread durability may have even gone down. If bikes had shown he same level of improvement as ca have, then those who want them could have fool proof bikes. And the racers could have the choice between the extra weight of a better chain or a light chain and the extra weight of a chain tool.
I've been riding on and off for 30 years plus, riding everyday (as good as) for the last 5 years, I've never had any bike component fail catastrophically apart from (and generally due to my own stupid fault) mech hangers, which is their reason for being.
I've had wear, I've had regular service changes of chains, cassettes and brake pads, so in my cycling life, I've suffered no catastrophic failures in 30 years, pretty difficult to find better reliability than that.
You do change the oil, the tyres, the spark plugs in your car no?
Changing a cassette and chain is exactly the same principle and probably costs less for parts and labour.
Consumable or sacrificial parts, with a service or recommended life, designed to provide the best trade off between practicality and durability and requiring regular replacement to prevent bigger further problems.
