Someone at a TV manufacturer realized they could technically tell the truth that there was a bigger dimension and put it on the box. It boosted sales, and then nearly every other manufacturer followed suit.
Does it actually do anything better? Not really.
Will it ever change? No. If a manufacturer didn’t do this, they would be seen as charging more for smaller TVs and it costs money to re-educate people that isn’t the case, easier to keep doing it.
This is a form of ratchet, and once the shift happens, it can’t go back. While ratchets come in all types, this is one of my least favorite because it doesn’t change anything about the product, or the customer experience, it’s a gimmick and not much more. It’s more powerful to find something that makes things better for the customer, particularly something that isn’t as easy to ratchet up as changing the label on a box.