Why wasn't code "managed" from the start? [closed]

Question

Note that this is not about the .NET CLR that Microsoft is thrusting into the atmosphere to evangelize the concept of managed code. Most of you know that managed code has been around for quite some time and isn't very related to rocket science.

What I would like to know is why the concept of runtime security in the evolution of computers came so late.

I know this is like asking "why didn't the first Model T Ford come with airbags and seat belts?". The relevance of the question still stands despite this though, because it's well within human nature to protect againts known dangers. E.g. the first T-Ford didn't go fast enough to motivate airbag research. It didn't go fast enough for people to make fatal judgemental errors so often that it would motivate seat belt as law and standard in many countries.

In computer evolution it's almost the other way around. We started out with assembler, the equivalent of driving a T-Ford at 200mph with an eye-patch. I've had the pleasure of conversating with a few old truckers from this era, hearing these stories about hand-assembling assembly code, human debuggers, grillion lines of code etc. If we make a really nasty error in C, we might end up with a bluescreen. Decades ago, you could end up with damaged hardware and god knows what. But it's a mystery to me - so many decades, and all we did to make crashing less painful was the bluescreen (sorry for using MS as archetype for anything).

It's not only within human nature to protect against known dangers, it's also within any programmer's nature to automate and systemize common facilities, like error checking, memory diagnostics, logging frameworks, backup maintenance etc etc.

Why didn't programmers/humans start to automate the task of ensuring that code they feed to the system won't harm the system?. Yes, ofcourse, performance. But hey, this was well before any seriously penetrating hardware standard. Why didn't motherboards get designed with bus architectures and extra processors to facilitate "managed code"?

Is there any metaphor to Model T Fords not being fast enough that I'm missing?