The sheer complexity of many of the systems we're building now really does make them necessary; so many programmers not just building but maintaining such complex systems over such long periods of time, now; the only way to be safe is to be safe.

There was a time when good drivers argued that seatbelts weren't strictly necessary if you knew what you were doing in a car, so there shouldn't be laws insisting on them.

So if by "strictly", you mean logically possible and sometimes within human ability; yeahbut we now just have to be more practical.

No doubt I should have narrowed the scope of the first sentence of my first post; but I'll leave it for now.

Not strictly necessary, but as the vast legions of merely adequate programmers have demonstrated they are practically necessary. They're necessary for scaling the number of programmers up.