Earlier quoted context omitted.
I think Valve should be sued over this, and lose. Sure, there will be clauses in their EULA stating that they aren't liable, but morally, those clauses should not be valid in any licensing agreement. Their commercial software caused damage to people, and they should pay through the nose for it.
There are several problems with your ideas. The most important one is that programmers only call themselves engineers until it comes time to take legal responsibility for their work; then suddenly they're artists creating works for hire. Programmers have worked very hard through the years to create the current liability-free environment; people die because of health care programming bugs, pilots crash because of avio…
In software, if I build a toy, and release it to the world, many people may find it useful. They might trust it with their most personal data, or vital business documents. But, it is still a toy.
If I build a toy bridge no-one tries to make it span the grand canyon. They see it for what it is - its faults are obvious. They try to cross my toy bridge and it easily collapses under the weight of their foot without costing the lives of anyone. And, if they somehow managed to string along my toy to the point where it could span the grand canyon, do you think anyone in their right mind would find me liable as the toy maker?
Ultimately, this is where the differences are huge. People are building toy bridges, pet bridges, foot bridges, bridges for single cars and bridges for 10 lanes of traffic. It's very difficult to accidentally substitute a bridge built for 1 person into a spot you need a bridge for 10 lanes of traffic.
But it's trivial in software to put a "toy bridge" or "pet bridge" where you need something like the golden gate bridge.
So, when someone takes my toy and tries to use it as the golden gate bridge, whose at fault?