Because you seem to be very confused on civil liabilities in most products. Manufactures are commonly held liable for the users use of products, for example look at any number of products that have caused injury.
Surely those are typically when the manufacturer was taken to have made an implicit promise of safety to the user and their surroundings, and the user got injured. If your fridge topples onto you and you get injured, the manufacturer might be liable; if you set up a trap where you topple your fridge onto a hapless passer-by, the manufacturer will probably not be liable towards them. Likewise with the classic McDonalds coffee spill liability story - I've yet to hear of a case of a coffee vendor being held liable over a deliberate attack where someone splashed someone else with hot coffee.
