I don't disagree with you, but the economic pressures are relentless. As late as the mid-1990s a manufacturer could count on there being an ecosystem and trained programmers available for the various high-security, high-reliability architectures on the market (or at least people willing to take jobs being trained as programmers, designers, etc for such systems). By 2000 those ecosystems and finally the architectures themselves had vanished under the avalanche of Wintel systems (bought a new PDP-11 lately? Or even a Tandem Nonstop?). And the cost differential in favor of Wintel went from 1/3x to 1/1000x. It is extremely hard to convince a product development board that your product needs 1000x more funding than the team building what is fundamentally very similar consumer- or commercial-grade system.
And the demand from customers drives things too. Right now every operating manager I work with wants to be able to monitor his plant from home on his iPhone. Customers are putting enormous pressure on their vendors to replace expensive proprietary (but secure) wireless interfaces with much cheaper iPhones. Security gets paid lip service in the spec but doesn't control the decision.
sPh