Because the fridge company can make more money by displaying ads on your fridge, and consumers can save more money by buying the fridge with the ads and taping cardboard in front.
Have any data that the savings are passed on to the consumer? I'm not saying you're wrong, I just don't see any modern, late-stage capitalism companies doing anything that actually benefits the consumer.
any instances of this in the wild? it seems like fridges are pretty cheap anyway and ones with smart features are more expensive? i don't think this a tv-like scenario.