First of all, the possibility of ice is obvious. No warning is needed. That is just silly.
Second of all, it wasn't just a light. It was a loud noise.
Third of all, the warning was delayed. It wouldn't occur right when starting the car. It often jolted me for attention right as I was pulling out into very busy traffic. The warning was a hazardous distraction.
Partly correct. Yes, the possibility may be in part obvious by conditions such as temperature. But I think most people who are used to driving on icy conditions can tell you that the ice may still come as a surprise. A system that could _reliably_ warn about slippery conditions would be good.
Somewhere where it snows once every 3 years it might be helpful. When you live in a place with real winter it actually makes you less safe since your brain has to spend time processing the alert for a condition that's obvious since the entire horizon is covered in a blanket of snow.
Which raises an interesting question: if a traction control system can detect poor traction conditions and compensate, couldn't it just as easily warn the driver to slow down, just like the backup radar on recent cars warns about pedestrians and cross traffic?
I used to own a VW which would turn on a light indicating a high chance of black ice when the temperature conditions lent themselves to that (black ice can form at several degrees above freezing temperature).
I suspect that a car could warn of low traction and recommend slowing down, but no car offers it because consumers won't buy a car that nags them to slow down, Even if it's for their own safety.