Ads benefit the customer by reducing the price of a 55" 4K TV down to 300 bucks, which is absolutely below the true cost of the device (parts, R&D, support etc).

They are selling you a below-cost TV and making it up in ads, same as Microsoft selling you a below-cost Xbox and making it up in accessory sales.

I don't think it's correct to say there's not benefit. The benefit of YouTube ads is that you have unlimited 4K content available for free (below cost of bandwidth).

While you may say you'll pay 600 bucks for that 55" TV with no ads, most consumers will disagree with you and they show it through behavior.