So your issue is you don't think people should have to think. Got it. In your world, there should only be two car manufacturers and they both produce one model. It's such a burden to have to make a decision.

PDPs, VAXes, and Alphas were widely used in manufacturing, telecommunications, DoD, financial institutions, and for numerous process control applications. It was not uncommon for VMS machines to run for 5+ years without a reboot. And VMS hardly qualifies as a 'simple OS design'. Clustering was available on VAXes LONG before Linux even existed. DECnet had some nice features to it as well (like transparent task-to-task communication). Having used Unix, Linux, and VMS for years, I would still take VMS any day (personal opinion here) in terms of ease of use, stability, security, and OS features. Too bad it hasn't seen any real development since the early 90s although it has been ported to the Itanium.