Freedom in principle is important in the US. Why can’t I sell a shoddy product? Why can’t I buy a shoddy product?
Also, warrantees force companies to bear the full cost of their negative externalities. In lots of markets, companies will come out ahead by not fixing or replacing your product (brand damage < actual damage), so those businesses are motivated directly into misleading consumers into buying worse products. Sounds obvious, but clearly that's not good for a society in the long run.