A friend in a momentary lapse of judgement ran a cutting torch across his arm... It did not occur to either of us to sue the equipment manufacturer..
How about a gun analogy. Guns are dangerous if used improperly. If you buy a gun and put it to your head and pull the trigger -- it's operator error. If you clean it without making sure the chamber is clear and shoot yourself in the foot -- operator error. Guns are dangerous if excessively worn or improperly maintained.
But what if you buy a new gun and it blows up in your face using standard commercial ammunition because the manufacturer made decisions based on marketing vs. safety. Not a specific problem with an individual weapon, but a known design flaw with the model. Lets make it lighter, the market wants that, and worry if the design can handle standard usage later. Soon, there were known failures, but the spreadsheet of profits vs. liability outweighed the risks. The gun was selling great and no other competitor offered one as light, at the same price, in the same caliber.
The previous accidents were covered up, and there was no reasonable way for the customer to know the company's product was any more dangerous than any other weapon. The now-blind customer had fired many rounds through many pistols, and had no reason to expect this brand new gun from an otherwise reputable manufacturer would cause any problems.
In the McDonald’s case the temperature was well above established norms for you, I or any commercial business. Injuries had occurred. But, a "flavor consultant" was listened to and a decision was made on sales vs. safety. Coffee is hot, you expect to spill some and expect to get a red spot maybe, or even a blister on the inside of your mouth on occasion. You do not expect to have the same result with coffee as you would with a blowtorch.
Charon
