In the case of the smart tv it's actually because you didn't really pay the full price of the tv. The manufacturer counts on the revenue from those ads to boost the tv profit margin to an acceptable level, otherwise they would have to charge you more for the tv initially.
If you don't believe me, look up the price of a "commercial display" comparable to your tv. And before anyone asks, the majority of customers would rather have a cheaper tv with ads in the menus than a more expensive one without.
I think that a good step would be to require a sizeable disclaimer on the box/marketing material stating that it is ad-supported/tracking-supported. That way it is much easier for consumers to know why the price is as cheap as it is.
Commercial displays are not more expensive because they don't have ads - that's an absurd suggestion. They are more expensive because they have higher requirements. They need to be running for at least 8 hours per day without issues, but often 24/7, as opposed to the usual 4-6. That's the main difference.
They also have to deal with direct sunlight and a wider range of thermal conditions. Commercial displays are often placed in shop windows, the panel needs to stand up to that, and the electronics need active cooling for when the chassis warms up.
If you don't believe me, look up the price of a "commercial display" comparable to your tv. And before anyone asks, the majority of customers would rather have a cheaper tv with ads in the menus than a more expensive one without.