Because a judge awarded an old lady a bunch because she spilled hot coffee on herself. If the judge says, you have to be careful because coffee is hot, and it isn't the restaurant's responsibility to warn you not to be stupid.
And if enough people don't like it, it will change.
If you're referring to the infamous McDonald's lawsuit, you should read up on what actually happened because you're citing an often repeated myth. You're parroting exactly what McDonald's wanted you to.
Here's a recap:
•The "old lady" admitted that the spill was her fault.
•Her issue was that the coffee was so hot, well beyond normal serving temperatures, that she suffered third degree burns on her legs and genitals the required extensive surgery.
•McDonald's served coffee at 190 degrees F. Coffee at that temperature causes 3rd degree burns in 3 to 7 seconds.
•The plaintiff didn't want to go to court. She wanted McDonald's to pay her medical expenses estimated at $20,000.
•McDonald's offered her $800.
•She obtained a lawyer, who offered to settle for $300,000. A mediator suggested $225,000. McDonald's rejected both offers.
•The jury (not judge) decided using comparative negligence that though the coffee has a warning, a reasonable person does not expect it to be a cup of near-boiling water, so they found McDonald's mostly responsible for the incident.
•The jury felt that McDonald's behavior was so dangerous and egregious that to send McDonald's a message, they recommended awarding the defendant $2.9 million.
•$200k was for compensatory damages, $2.7 million was punitive, a number they arrived at as an estimated two days of McDonald's coffee revenues.
•The plaintiff later settled for somewhere under $600,000.
•McDonald's reduced the temperature it serves coffee.