0% financing is a form of discount -- the seller loses money offering it since they have to administer the loan and take legal action if you default, plus monthly payments are worth less than up-front payment thanks to inflation and the time value of money.

Sellers offer discounts when they're worried about moving product. Stern and the other manufacturers are selling all they can make and then some (production backlogs are months to years long across the industry). That's not the kind of market that encourages sellers to offer discounts.