Not all customers are thick but considering that there are a great number of car owners/drivers with lack of simple technical knowledge on cars. Since the product is freely available on the shelf, can be purchased by any customer. such precautions are added for that reason.
I buy Forte Motor Flush from a shop here and once a new seller was behind the desk. He asked me if I know that the product is poured inn engine oil and I must not drive the car with it added to engine oil

I said thanks for the information and I didn't take it as personal.
Another example: Several years ago at a gas station a woman driver in the next gas filling place approached me with a liter of oil in her hand, asking me if can show where that product should be poured

I recognized that she was actually our cities newly elected member of the parliament

So I showed the place under the hood and even checked the oil level and added new oil.
Believe it or not but the spectrum of the drivers are extremely wide.