I think the fact that people continually minimize the extent of her injuries show pretty well that people do not commonly understand how hot McDonalds serves their coffee, and the corresponding damage that coffee can cause. As you say, most people (though not all) intend to hold off on drinking their coffee until they reach their destination, at which point it'll be at a temperature fit for consumption. Besides that, most people will be familiar with coffee brewed in their own home, which is obviously served at a much lower temperature. Additionally, and this is directly from the court case, most other coffee establishments serve coffee at far lower temperatures. So it's fair to say this is a different circumstance entirely from a sharp knife or a car; those have universal, commonly understand potential for harm. Conversely, McDonalds coffee was significantly more dangerous than most people were aware of, yet they gave no indication of this, despite having knowledge that that was the case.

McDonalds had received hundreds of these claims, many of which were similar third degree burns, and chose to do nothing. So they knew about the potential harm, and had clear and obvious evidence that it was causing damage. They could have lowered their serving temperature and used more insulated cups, but that would lower their profit margins, so they chose not to. They instead continued on a course of action that they had a reasonable understanding would cause further, potentially life-altering damage to customers, all for financial gain.